On Thu, 07 Jun 2012 16:49:10 -0700, John Larkin
wrote:

On Wed, 06 Jun 2012 15:31:57 -0700, Jim Thompson
wrote:

[snip]

****es lots of people off, when I instantly say, "Can't be" :-)

...Jim Thompson

Gosh, you are wonderful. Tell us more about how smart you are, how you
know everything, and how much you enjoy ****ing off people who aren't
as smart as you are. Are who aren't the superb marksman (at 30 feet)
that you are.

You really ought to sweat that, John "Dog Turd" Larkin ;-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Thu, 07 Jun 2012 17:16:02 -0700, Jim Thompson
wrote:

On Thu, 07 Jun 2012 16:45:20 -0700, John Larkin
wrote:

On Thu, 7 Jun 2012 21:54:21 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote in
message ...
On Thu, 7 Jun 2012 15:32:20 -0500, "Dave" wrote:


"Jim Thompson" wrote
in
message ...
On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
wrote:


Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
wrote:


Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave"
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave


Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current
in
their approach to design. They approach it with the rule of thumb that
the
input impedance should be 10x the output impedance of the previous
stage.
Similar. (The input impedance of the OP's stages are only slightly
higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing.
Or
is everything just optimized by multi-variable calculus?

I don't know if there are "rules of thumb"... maybe just calculate
rather than doing a NOLA white-trash guess ?:-)

...Jim Thompson


Does it really make you feel good to talk that way about other people,
calling someone you don't know a POS, and white-trash? Personally, I
think
it says a lot more about you than it does about me.

And no, I don't know anything about the calculations involved in anything
as
simple as an audio amp. Like I said, I'm making this up as I go along. I
don't know anything. I'm just trying to learn.

Dave


I tried to help, suggesting you calculate the bias currents. Rather
than asking what I meant, if you're "just trying to learn", you
smart-mouthed.

And I don't respond well to smart-mouthed brats... it's enough of a
problem to deal with Larkin ;-)


You declared war on JL by being a spitefull old fart.

Take care now - you're way past fighting on 2 fronts.


Look at his posts. Nothing but boasting about how smart he is, how
many things he's done, how many great ideas he has. But no content, no
help, nothing but the occasional Spice graphs from who-knows-what
secret circuits. He apparently expects all deference due to a
self-declared "Master Circuit Designer" and gets all hen-squawkey when
he doesn't get it. He doesn't seem to be interested in electronics at
all.

He doesn't "try to help", he just tries to inflate his ego. It's not
working. Sad excuse for "war."

So sayeth John "Dog Turd" Larkin ;-)

...Jim Thompson


You must be one of those usenet pain sluts, the sort of person who
craves public humiliation. On the other hand, you may just be a silly
old fool. Most likely, old fool.


--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

On Thu, 07 Jun 2012 17:18:38 -0700, Jim Thompson
wrote:

On Thu, 07 Jun 2012 16:49:10 -0700, John Larkin
wrote:

On Wed, 06 Jun 2012 15:31:57 -0700, Jim Thompson
wrote:

[snip]

****es lots of people off, when I instantly say, "Can't be" :-)

...Jim Thompson

Gosh, you are wonderful. Tell us more about how smart you are, how you
know everything, and how much you enjoy ****ing off people who aren't
as smart as you are. Are who aren't the superb marksman (at 30 feet)
that you are.

You really ought to sweat that, John "Dog Turd" Larkin ;-)

...Jim Thompson

Sweat what? Say it.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

On Thu, 07 Jun 2012 18:07:20 -0700, John Larkin
wrote:

On Thu, 07 Jun 2012 17:16:02 -0700, Jim Thompson
wrote:

On Thu, 07 Jun 2012 16:45:20 -0700, John Larkin
wrote:

On Thu, 7 Jun 2012 21:54:21 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote in
message ...
On Thu, 7 Jun 2012 15:32:20 -0500, "Dave" wrote:


"Jim Thompson" wrote
in
message ...
On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
wrote:


Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
wrote:


Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave"
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave


Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current
in
their approach to design. They approach it with the rule of thumb that
the
input impedance should be 10x the output impedance of the previous
stage.
Similar. (The input impedance of the OP's stages are only slightly
higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing.
Or
is everything just optimized by multi-variable calculus?

I don't know if there are "rules of thumb"... maybe just calculate
rather than doing a NOLA white-trash guess ?:-)

...Jim Thompson


Does it really make you feel good to talk that way about other people,
calling someone you don't know a POS, and white-trash? Personally, I
think
it says a lot more about you than it does about me.

And no, I don't know anything about the calculations involved in anything
as
simple as an audio amp. Like I said, I'm making this up as I go along. I
don't know anything. I'm just trying to learn.

Dave


I tried to help, suggesting you calculate the bias currents. Rather
than asking what I meant, if you're "just trying to learn", you
smart-mouthed.

And I don't respond well to smart-mouthed brats... it's enough of a
problem to deal with Larkin ;-)


You declared war on JL by being a spitefull old fart.

Take care now - you're way past fighting on 2 fronts.


Look at his posts. Nothing but boasting about how smart he is, how
many things he's done, how many great ideas he has. But no content, no
help, nothing but the occasional Spice graphs from who-knows-what
secret circuits. He apparently expects all deference due to a
self-declared "Master Circuit Designer" and gets all hen-squawkey when
he doesn't get it. He doesn't seem to be interested in electronics at
all.

He doesn't "try to help", he just tries to inflate his ego. It's not
working. Sad excuse for "war."

So sayeth John "Dog Turd" Larkin ;-)

...Jim Thompson


You must be one of those usenet pain sluts, the sort of person who
craves public humiliation. On the other hand, you may just be a silly
old fool. Most likely, old fool.

Designed any "cool" circuits lately ?:-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Thu, 07 Jun 2012 19:15:42 -0700, Jim Thompson
wrote:

On Thu, 07 Jun 2012 18:07:20 -0700, John Larkin
wrote:

On Thu, 07 Jun 2012 17:16:02 -0700, Jim Thompson
wrote:

On Thu, 07 Jun 2012 16:45:20 -0700, John Larkin
wrote:

On Thu, 7 Jun 2012 21:54:21 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote in
message ...
On Thu, 7 Jun 2012 15:32:20 -0500, "Dave" wrote:


"Jim Thompson" wrote
in
message ...
On Tue, 5 Jun 2012 22:12:30 -0400, "Tom Del Rosso"
wrote:


Jim Thompson wrote:
On Tue, 5 Jun 2012 18:28:22 -0400, "Tom Del Rosso"
wrote:


Jim Thompson wrote:
On Wed, 23 May 2012 15:40:17 -0500, "Dave"
wrote:

Posted a while back about a project I am trying to concoct- an
intercom for my front door- and have made some progress.
Unfortunately I hit a speed bump when I added transistor Q4.
Now it only gives me noise at the output, and lots and lots of
that. Capacitors are all 100uF 35V, which I am thinking may be
the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it
with a 2N5296 from my junkbox, but that just doubled the volume
of the noisy output. If anyone sees something I should but
don't, please post. The only thing I can think of is upping the
voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave


Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

In my head, it's 14ma. That can't be right. The calc concurs. Is
that a little bit too much?

Aren't the emitter caps about 10 times as big as needed?

Ian did notice that he was just throwing gain at the problem though.

Yep, I was stunned... Ian said something cogent. But his buddy, Dave,
is beyond all hope... rude little POS.

I don't have AoE in reach, but I don't think they mention bias current
in
their approach to design. They approach it with the rule of thumb that
the
input impedance should be 10x the output impedance of the previous
stage.
Similar. (The input impedance of the OP's stages are only slightly
higher
than the previous output impedance.)

I'd like to know if you use any rules of thumb for this sort of thing.
Or
is everything just optimized by multi-variable calculus?

I don't know if there are "rules of thumb"... maybe just calculate
rather than doing a NOLA white-trash guess ?:-)

...Jim Thompson


Does it really make you feel good to talk that way about other people,
calling someone you don't know a POS, and white-trash? Personally, I
think
it says a lot more about you than it does about me.

And no, I don't know anything about the calculations involved in anything
as
simple as an audio amp. Like I said, I'm making this up as I go along. I
don't know anything. I'm just trying to learn.

Dave


I tried to help, suggesting you calculate the bias currents. Rather
than asking what I meant, if you're "just trying to learn", you
smart-mouthed.

And I don't respond well to smart-mouthed brats... it's enough of a
problem to deal with Larkin ;-)


You declared war on JL by being a spitefull old fart.

Take care now - you're way past fighting on 2 fronts.


Look at his posts. Nothing but boasting about how smart he is, how
many things he's done, how many great ideas he has. But no content, no
help, nothing but the occasional Spice graphs from who-knows-what
secret circuits. He apparently expects all deference due to a
self-declared "Master Circuit Designer" and gets all hen-squawkey when
he doesn't get it. He doesn't seem to be interested in electronics at
all.

He doesn't "try to help", he just tries to inflate his ego. It's not
working. Sad excuse for "war."

So sayeth John "Dog Turd" Larkin ;-)

...Jim Thompson


You must be one of those usenet pain sluts, the sort of person who
craves public humiliation. On the other hand, you may just be a silly
old fool. Most likely, old fool.

Designed any "cool" circuits lately ?:-)

...Jim Thompson

Yeah, this week I'm designing a small box, Ethernet, 5-channel
timestamper with 12 ps LSB resolution. It's for a national lab, boom
boys, but I'm putting in hooks and DRAM so it could do TOF histograms
or 2D delay-line imaging.

I get the first article of a new 10-amp NMR gradient driver to test
next week, and we're just finishing the embedded uP code for our
USB-based picosecond pulse generator.

http://www.highlandtechnology.com/DSS/T240DS.shtml

Look at that last view, #4. That is 100 ps/div, about the flattest,
cleanest pulse you'll ever see at this speed. The bullet says the
rise/fall times are 60 ps, but that's because we measure 10/90. Most
people in the picosecond business use 20/80, and by that standard our
edges are more like 40 ps. First unit ships on Monday if we finish all
the calibration software.

Those are all my designs. My guys have a few other things going: a
synchro/resolver/LVDT thing, two separate OEM laser controllers, and
some small stuff.

How about you? Keeping busy? Loading your own ammo?


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

"John Larkin" wrote in message
...

Yeah, this week I'm designing a small box, Ethernet, 5-channel
timestamper with 12 ps LSB resolution. It's for a national lab, boom
boys, but I'm putting in hooks and DRAM so it could do TOF histograms
or 2D delay-line imaging.

I get the first article of a new 10-amp NMR gradient driver to test
next week, and we're just finishing the embedded uP code for our
USB-based picosecond pulse generator.

http://www.highlandtechnology.com/DSS/T240DS.shtml

Look at that last view, #4. That is 100 ps/div, about the flattest,
cleanest pulse you'll ever see at this speed. The bullet says the
rise/fall times are 60 ps, but that's because we measure 10/90. Most
people in the picosecond business use 20/80, and by that standard our
edges are more like 40 ps. First unit ships on Monday if we finish all
the calibration software.


Five ohm output impedance? Does that cause any reflections when doing TDR?

tm

On 6/7/2012 9:38 PM, flipper wrote:
On Thu, 07 Jun 2012 13:42:13 -0700, Jim Thompson
wrote:

On Thu, 7 Jun 2012 15:32:20 -0500, "Dave" wrote:




Does it really make you feel good to talk that way about other people,
calling someone you don't know a POS, and white-trash? Personally, I think
it says a lot more about you than it does about me.

And no, I don't know anything about the calculations involved in anything as
simple as an audio amp. Like I said, I'm making this up as I go along. I
don't know anything. I'm just trying to learn.

Dave


I tried to help, suggesting you calculate the bias currents. Rather
than asking what I meant, if you're "just trying to learn", you
smart-mouthed.

And I don't respond well to smart-mouthed brats... it's enough of a
problem to deal with Larkin ;-)

HOWEVER... If you are really "just trying to learn", calculate the
bias as I suggested... why is it so high? And how much gain do you
really need? Put some numbers on things, and I'll try to point you in
the right direction.

For really, I'll help... but take the chip off your shoulder.

...Jim Thompson

Frankly, Jim, I think you've become so attuned to trading barbs with
'whoever' that the 'chip', so to speak, is on your shoulder and you
misinterpreted his lack of knowledge as 'smart mouthed'.

He said from day one he knows next to nothing so when you toss out
what are to you 'blindingly obvious' things like "bias current" he
doesn't know what you mean because, as he explained, 'to him' bias is
a voltage. That not being "smart mouthed," it's just all he knows from
what he's managed to 'pick up' from somewhere.

I suspect you're used to 'challenging' EEs to 'think' but that isn't
going to work here because he isn't an EE and will likely not
understand what you're asking. You need to 'explain' things to him,
not ask him to 'explain' it to you expecting that, in doing so, the
'light bulb' will go off and he'll 'realize' where you're going and
the thing he's overlooked.

+1. As a casual observer and infrequent poster, I agree with flipper's
assessment. It appears to me that Jim is behaving with the
characteristics of a pompous a**; not that he necessarily is one, but he
very well could be.

On Fri, 8 Jun 2012 00:04:13 -0400, "tm"
wrote:


"John Larkin" wrote in message
.. .

Yeah, this week I'm designing a small box, Ethernet, 5-channel
timestamper with 12 ps LSB resolution. It's for a national lab, boom
boys, but I'm putting in hooks and DRAM so it could do TOF histograms
or 2D delay-line imaging.

I get the first article of a new 10-amp NMR gradient driver to test
next week, and we're just finishing the embedded uP code for our
USB-based picosecond pulse generator.

http://www.highlandtechnology.com/DSS/T240DS.shtml

Look at that last view, #4. That is 100 ps/div, about the flattest,
cleanest pulse you'll ever see at this speed. The bullet says the
rise/fall times are 60 ps, but that's because we measure 10/90. Most
people in the picosecond business use 20/80, and by that standard our
edges are more like 40 ps. First unit ships on Monday if we finish all
the calibration software.


Five ohm output impedance? Does that cause any reflections when doing TDR?

tm

It's not for doing TDR. It's main use will be to drive amplifiers that
in turn drive lasers or E/O modulators. I assume the thing I'm driving
is a 50 ohm load. I could make it 50 ohms, but that would cut the max
amplitude in half.

Next generation, I want to do at least 6 volts, truly 50 ohms... if I
can find a driver circuit that can do it. Then I could drive E/O
modulators directly.






--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

On Thu, 07 Jun 2012 22:36:56 -0700, RosemontCrest
wrote:

On 6/7/2012 9:38 PM, flipper wrote:
On Thu, 07 Jun 2012 13:42:13 -0700, Jim Thompson
wrote:

On Thu, 7 Jun 2012 15:32:20 -0500, "Dave" wrote:




Does it really make you feel good to talk that way about other people,
calling someone you don't know a POS, and white-trash? Personally, I think
it says a lot more about you than it does about me.

And no, I don't know anything about the calculations involved in anything as
simple as an audio amp. Like I said, I'm making this up as I go along. I
don't know anything. I'm just trying to learn.

Dave


I tried to help, suggesting you calculate the bias currents. Rather
than asking what I meant, if you're "just trying to learn", you
smart-mouthed.

And I don't respond well to smart-mouthed brats... it's enough of a
problem to deal with Larkin ;-)

HOWEVER... If you are really "just trying to learn", calculate the
bias as I suggested... why is it so high? And how much gain do you
really need? Put some numbers on things, and I'll try to point you in
the right direction.

For really, I'll help... but take the chip off your shoulder.

...Jim Thompson

Frankly, Jim, I think you've become so attuned to trading barbs with
'whoever' that the 'chip', so to speak, is on your shoulder and you
misinterpreted his lack of knowledge as 'smart mouthed'.

He said from day one he knows next to nothing so when you toss out
what are to you 'blindingly obvious' things like "bias current" he
doesn't know what you mean because, as he explained, 'to him' bias is
a voltage. That not being "smart mouthed," it's just all he knows from
what he's managed to 'pick up' from somewhere.

I suspect you're used to 'challenging' EEs to 'think' but that isn't
going to work here because he isn't an EE and will likely not
understand what you're asking. You need to 'explain' things to him,
not ask him to 'explain' it to you expecting that, in doing so, the
'light bulb' will go off and he'll 'realize' where you're going and
the thing he's overlooked.

+1. As a casual observer and infrequent poster, I agree with flipper's
assessment. It appears to me that Jim is behaving with the
characteristics of a pompous a**; not that he necessarily is one, but he
very well could be.



He is!


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

"John Larkin" wrote in message
...
On Fri, 8 Jun 2012 00:04:13 -0400, "tm"
wrote:


"John Larkin" wrote in
message
. ..

Yeah, this week I'm designing a small box, Ethernet, 5-channel
timestamper with 12 ps LSB resolution. It's for a national lab, boom
boys, but I'm putting in hooks and DRAM so it could do TOF histograms
or 2D delay-line imaging.

I get the first article of a new 10-amp NMR gradient driver to test
next week, and we're just finishing the embedded uP code for our
USB-based picosecond pulse generator.

http://www.highlandtechnology.com/DSS/T240DS.shtml

Look at that last view, #4. That is 100 ps/div, about the flattest,
cleanest pulse you'll ever see at this speed. The bullet says the
rise/fall times are 60 ps, but that's because we measure 10/90. Most
people in the picosecond business use 20/80, and by that standard our
edges are more like 40 ps. First unit ships on Monday if we finish all
the calibration software.


Five ohm output impedance? Does that cause any reflections when doing TDR?

tm

It's not for doing TDR. It's main use will be to drive amplifiers that
in turn drive lasers or E/O modulators. I assume the thing I'm driving
is a 50 ohm load. I could make it 50 ohms, but that would cut the max
amplitude in half.

Next generation, I want to do at least 6 volts, truly 50 ohms... if I
can find a driver circuit that can do it. Then I could drive E/O
modulators directly.



That makes sense. I just wasn't sure you didn't have a typo in the specs. If
there is a mismatch on the end of a cable, it could reflect back to the
pulse generator and be re-reflected off the five ohm mismatch.

I like the packaging.

tm

On Fri, 8 Jun 2012 10:56:36 -0400, "tm"
wrote:


"John Larkin" wrote in message
.. .
On Fri, 8 Jun 2012 00:04:13 -0400, "tm"
wrote:


"John Larkin" wrote in
message
...

Yeah, this week I'm designing a small box, Ethernet, 5-channel
timestamper with 12 ps LSB resolution. It's for a national lab, boom
boys, but I'm putting in hooks and DRAM so it could do TOF histograms
or 2D delay-line imaging.

I get the first article of a new 10-amp NMR gradient driver to test
next week, and we're just finishing the embedded uP code for our
USB-based picosecond pulse generator.

http://www.highlandtechnology.com/DSS/T240DS.shtml

Look at that last view, #4. That is 100 ps/div, about the flattest,
cleanest pulse you'll ever see at this speed. The bullet says the
rise/fall times are 60 ps, but that's because we measure 10/90. Most
people in the picosecond business use 20/80, and by that standard our
edges are more like 40 ps. First unit ships on Monday if we finish all
the calibration software.


Five ohm output impedance? Does that cause any reflections when doing TDR?

tm

It's not for doing TDR. It's main use will be to drive amplifiers that
in turn drive lasers or E/O modulators. I assume the thing I'm driving
is a 50 ohm load. I could make it 50 ohms, but that would cut the max
amplitude in half.

Next generation, I want to do at least 6 volts, truly 50 ohms... if I
can find a driver circuit that can do it. Then I could drive E/O
modulators directly.



That makes sense. I just wasn't sure you didn't have a typo in the specs. If
there is a mismatch on the end of a cable, it could reflect back to the
pulse generator and be re-reflected off the five ohm mismatch.

I like the packaging.

tm


The box is a standard Hammond enclosure. You see them (or possibly
their clones) everywhere nowadays. Nice box, very EMI tight.

This is the PC board:

https://dl.dropbox.com/u/53724080/PC...irst_Board.JPG

Frankly, the hardest part was getting the signals out of U8 (on the
right) into the edge-launch SMA connectors, trying to keep a clean
fast 50 ohm path. Rob and I did dueling EM simulations (ATLC under
Linux, ATLC2 under Windows respectively) of the connector and PCB
stackup, and it came out pretty good, some unknown mix of wisdom and
dumb luck.

https://dl.dropbox.com/u/53724080/ATLC/T240.jpg

https://dl.dropbox.com/u/53724080/ATLC/E-field.jpg


There is a small inductive glitch at the connector/PCB transition, as
TDRd on the actual board. ATLC, being a 2D simulator, isn't up to
stuff like this. I'm theorizing that's caused by a tiny gap between
the connector PCB pads and the edge of the board. The fix would be to
move the connector footprint about 20 mils to the right. Then the PC
house would be cutting away copper when they route the board outline,
which means they would probably call us and tell us that we did the
layout wrong, and we'd have to tell them to go ahead and cut the
copper.

Some day I should lay out a board with maybe a dozen edge-launch
variations, just to find the best one.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

"John Larkin" wrote in message
...
On Fri, 8 Jun 2012 10:56:36 -0400, "tm"
wrote:


"John Larkin" wrote in
message
. ..
On Fri, 8 Jun 2012 00:04:13 -0400, "tm"
wrote:


"John Larkin" wrote in
message
m...

Yeah, this week I'm designing a small box, Ethernet, 5-channel
timestamper with 12 ps LSB resolution. It's for a national lab, boom
boys, but I'm putting in hooks and DRAM so it could do TOF histograms
or 2D delay-line imaging.

I get the first article of a new 10-amp NMR gradient driver to test
next week, and we're just finishing the embedded uP code for our
USB-based picosecond pulse generator.

http://www.highlandtechnology.com/DSS/T240DS.shtml

Look at that last view, #4. That is 100 ps/div, about the flattest,
cleanest pulse you'll ever see at this speed. The bullet says the
rise/fall times are 60 ps, but that's because we measure 10/90. Most
people in the picosecond business use 20/80, and by that standard our
edges are more like 40 ps. First unit ships on Monday if we finish all
the calibration software.


Five ohm output impedance? Does that cause any reflections when doing
TDR?

tm

It's not for doing TDR. It's main use will be to drive amplifiers that
in turn drive lasers or E/O modulators. I assume the thing I'm driving
is a 50 ohm load. I could make it 50 ohms, but that would cut the max
amplitude in half.

Next generation, I want to do at least 6 volts, truly 50 ohms... if I
can find a driver circuit that can do it. Then I could drive E/O
modulators directly.



That makes sense. I just wasn't sure you didn't have a typo in the specs.
If
there is a mismatch on the end of a cable, it could reflect back to the
pulse generator and be re-reflected off the five ohm mismatch.

I like the packaging.

tm


The box is a standard Hammond enclosure. You see them (or possibly
their clones) everywhere nowadays. Nice box, very EMI tight.

This is the PC board:

https://dl.dropbox.com/u/53724080/PC...irst_Board.JPG

Frankly, the hardest part was getting the signals out of U8 (on the
right) into the edge-launch SMA connectors, trying to keep a clean
fast 50 ohm path. Rob and I did dueling EM simulations (ATLC under
Linux, ATLC2 under Windows respectively) of the connector and PCB
stackup, and it came out pretty good, some unknown mix of wisdom and
dumb luck.

https://dl.dropbox.com/u/53724080/ATLC/T240.jpg

https://dl.dropbox.com/u/53724080/ATLC/E-field.jpg


There is a small inductive glitch at the connector/PCB transition, as
TDRd on the actual board. ATLC, being a 2D simulator, isn't up to
stuff like this. I'm theorizing that's caused by a tiny gap between
the connector PCB pads and the edge of the board. The fix would be to
move the connector footprint about 20 mils to the right. Then the PC
house would be cutting away copper when they route the board outline,
which means they would probably call us and tell us that we did the
layout wrong, and we'd have to tell them to go ahead and cut the
copper.

Some day I should lay out a board with maybe a dozen edge-launch
variations, just to find the best one.



Why not just notch the board 20 mils to move the connector in closer. You
can then put a lock washer between the flange and the case. Might also
solder the ground plane all the way across the connector in addition to the
pins.

Doing a test board would be an interesting experiment.

On Thu, 07 Jun 2012 23:38:42 -0500, flipper wrote:

On Thu, 07 Jun 2012 13:42:13 -0700, Jim Thompson
wrote:

On Thu, 7 Jun 2012 15:32:20 -0500, "Dave" wrote:




Does it really make you feel good to talk that way about other people,
calling someone you don't know a POS, and white-trash? Personally, I think
it says a lot more about you than it does about me.

And no, I don't know anything about the calculations involved in anything as
simple as an audio amp. Like I said, I'm making this up as I go along. I
don't know anything. I'm just trying to learn.

Dave


I tried to help, suggesting you calculate the bias currents. Rather
than asking what I meant, if you're "just trying to learn", you
smart-mouthed.

And I don't respond well to smart-mouthed brats... it's enough of a
problem to deal with Larkin ;-)

HOWEVER... If you are really "just trying to learn", calculate the
bias as I suggested... why is it so high? And how much gain do you
really need? Put some numbers on things, and I'll try to point you in
the right direction.

For really, I'll help... but take the chip off your shoulder.

...Jim Thompson

Frankly, Jim, I think you've become so attuned to trading barbs with
'whoever' that the 'chip', so to speak, is on your shoulder and you
misinterpreted his lack of knowledge as 'smart mouthed'.

He said from day one he knows next to nothing so when you toss out
what are to you 'blindingly obvious' things like "bias current" he
doesn't know what you mean because, as he explained, 'to him' bias is
a voltage. That not being "smart mouthed," it's just all he knows from
what he's managed to 'pick up' from somewhere.

I suspect you're used to 'challenging' EEs to 'think' but that isn't
going to work here because he isn't an EE and will likely not
understand what you're asking. You need to 'explain' things to him,
not ask him to 'explain' it to you expecting that, in doing so, the
'light bulb' will go off and he'll 'realize' where you're going and
the thing he's overlooked.

So, what should I do, just design it for him?

But you're correct, maybe I nudged Dave like I would an engineer, but
isn't this mild...

[JT]

"Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

How much voltage gain do you need?

What is the load impedance? Is it a speaker?"

[Dave]

"Don't mean to be critical, but these seem like very generic"
questions."

==

What the hell does that mean?

Nothing like, "How...", or an answer to my gain question.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Thu, 07 Jun 2012 22:36:56 -0700, RosemontCrest
wrote:

On 6/7/2012 9:38 PM, flipper wrote:
On Thu, 07 Jun 2012 13:42:13 -0700, Jim Thompson
wrote:

On Thu, 7 Jun 2012 15:32:20 -0500, "Dave" wrote:




Does it really make you feel good to talk that way about other people,
calling someone you don't know a POS, and white-trash? Personally, I think
it says a lot more about you than it does about me.

And no, I don't know anything about the calculations involved in anything as
simple as an audio amp. Like I said, I'm making this up as I go along. I
don't know anything. I'm just trying to learn.

Dave


I tried to help, suggesting you calculate the bias currents. Rather
than asking what I meant, if you're "just trying to learn", you
smart-mouthed.

And I don't respond well to smart-mouthed brats... it's enough of a
problem to deal with Larkin ;-)

HOWEVER... If you are really "just trying to learn", calculate the
bias as I suggested... why is it so high? And how much gain do you
really need? Put some numbers on things, and I'll try to point you in
the right direction.

For really, I'll help... but take the chip off your shoulder.

...Jim Thompson

Frankly, Jim, I think you've become so attuned to trading barbs with
'whoever' that the 'chip', so to speak, is on your shoulder and you
misinterpreted his lack of knowledge as 'smart mouthed'.

He said from day one he knows next to nothing so when you toss out
what are to you 'blindingly obvious' things like "bias current" he
doesn't know what you mean because, as he explained, 'to him' bias is
a voltage. That not being "smart mouthed," it's just all he knows from
what he's managed to 'pick up' from somewhere.

I suspect you're used to 'challenging' EEs to 'think' but that isn't
going to work here because he isn't an EE and will likely not
understand what you're asking. You need to 'explain' things to him,
not ask him to 'explain' it to you expecting that, in doing so, the
'light bulb' will go off and he'll 'realize' where you're going and
the thing he's overlooked.

+1. As a casual observer and infrequent poster, I agree with flipper's
assessment. It appears to me that Jim is behaving with the
characteristics of a pompous a**; not that he necessarily is one, but he
very well could be.


I try, as best as I can ;-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Fri, 8 Jun 2012 12:14:57 -0400, "tm"
wrote:


"John Larkin" wrote in message
.. .
On Fri, 8 Jun 2012 10:56:36 -0400, "tm"
wrote:


"John Larkin" wrote in
message
...
On Fri, 8 Jun 2012 00:04:13 -0400, "tm"
wrote:


"John Larkin" wrote in
message
om...

Yeah, this week I'm designing a small box, Ethernet, 5-channel
timestamper with 12 ps LSB resolution. It's for a national lab, boom
boys, but I'm putting in hooks and DRAM so it could do TOF histograms
or 2D delay-line imaging.

I get the first article of a new 10-amp NMR gradient driver to test
next week, and we're just finishing the embedded uP code for our
USB-based picosecond pulse generator.

http://www.highlandtechnology.com/DSS/T240DS.shtml

Look at that last view, #4. That is 100 ps/div, about the flattest,
cleanest pulse you'll ever see at this speed. The bullet says the
rise/fall times are 60 ps, but that's because we measure 10/90. Most
people in the picosecond business use 20/80, and by that standard our
edges are more like 40 ps. First unit ships on Monday if we finish all
the calibration software.


Five ohm output impedance? Does that cause any reflections when doing
TDR?

tm

It's not for doing TDR. It's main use will be to drive amplifiers that
in turn drive lasers or E/O modulators. I assume the thing I'm driving
is a 50 ohm load. I could make it 50 ohms, but that would cut the max
amplitude in half.

Next generation, I want to do at least 6 volts, truly 50 ohms... if I
can find a driver circuit that can do it. Then I could drive E/O
modulators directly.



That makes sense. I just wasn't sure you didn't have a typo in the specs.
If
there is a mismatch on the end of a cable, it could reflect back to the
pulse generator and be re-reflected off the five ohm mismatch.

I like the packaging.

tm


The box is a standard Hammond enclosure. You see them (or possibly
their clones) everywhere nowadays. Nice box, very EMI tight.

This is the PC board:

https://dl.dropbox.com/u/53724080/PC...irst_Board.JPG

Frankly, the hardest part was getting the signals out of U8 (on the
right) into the edge-launch SMA connectors, trying to keep a clean
fast 50 ohm path. Rob and I did dueling EM simulations (ATLC under
Linux, ATLC2 under Windows respectively) of the connector and PCB
stackup, and it came out pretty good, some unknown mix of wisdom and
dumb luck.

https://dl.dropbox.com/u/53724080/ATLC/T240.jpg

https://dl.dropbox.com/u/53724080/ATLC/E-field.jpg


There is a small inductive glitch at the connector/PCB transition, as
TDRd on the actual board. ATLC, being a 2D simulator, isn't up to
stuff like this. I'm theorizing that's caused by a tiny gap between
the connector PCB pads and the edge of the board. The fix would be to
move the connector footprint about 20 mils to the right. Then the PC
house would be cutting away copper when they route the board outline,
which means they would probably call us and tell us that we did the
layout wrong, and we'd have to tell them to go ahead and cut the
copper.

Some day I should lay out a board with maybe a dozen edge-launch
variations, just to find the best one.



Why not just notch the board 20 mils to move the connector in closer.

The board is notched, but only to clear the end-plate on the box. The
real issue is whether the footprint of the connector goes all the way
to the edge of the board. For that to happen, we really have to cut
copper when the fab shop routes the board. No big deal, I'll do that
next time.

You
can then put a lock washer between the flange and the case. Might also
solder the ground plane all the way across the connector in addition to the
pins.


The layer 2 ground plane is deliberately cut out, under the connector,
to control the impedance. There is a solid ground pour on layer 4, the
bottom, between the connector tangs, but there's not much e-field down
there so that doesn't matter much.

Doing a test board would be an interesting experiment.

Yeah, I accumulate ideas and unknowns and, every once in a while,
throw them onto a 4-layer board and have a few fabbed. Throw in a few
test microstrips, filter layouts, connector adapters, whatever.

Somebody with time could accumulate layout bits from various people
and do a layout, shear it up into sections, and distribute. People
could share the fab expense.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

On Wed, 23 May 2012 15:40:17 -0500, "Dave" wrote:

Posted a while back about a project I am trying to concoct- an intercom for
my front door- and have made some progress. Unfortunately I hit a speed
bump when I added transistor Q4. Now it only gives me noise at the output,
and lots and lots of that. Capacitors are all 100uF 35V, which I am
thinking may be the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it with a 2N5296
from my junkbox, but that just doubled the volume of the noisy output. If
anyone sees something I should but don't, please post. The only thing I can
think of is upping the voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave


Look over this page for some ideas...

http://www.next.gr/telephone/intercom-circuits/

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Fri, 08 Jun 2012 15:30:03 -0500, flipper wrote:

On Fri, 08 Jun 2012 09:31:33 -0700, Jim Thompson
wrote:

On Thu, 07 Jun 2012 23:38:42 -0500, flipper wrote:


Frankly, Jim, I think you've become so attuned to trading barbs with
'whoever' that the 'chip', so to speak, is on your shoulder and you
misinterpreted his lack of knowledge as 'smart mouthed'.

He said from day one he knows next to nothing so when you toss out
what are to you 'blindingly obvious' things like "bias current" he
doesn't know what you mean because, as he explained, 'to him' bias is
a voltage. That not being "smart mouthed," it's just all he knows from
what he's managed to 'pick up' from somewhere.

I suspect you're used to 'challenging' EEs to 'think' but that isn't
going to work here because he isn't an EE and will likely not
understand what you're asking. You need to 'explain' things to him,
not ask him to 'explain' it to you expecting that, in doing so, the
'light bulb' will go off and he'll 'realize' where you're going and
the thing he's overlooked.

So, what should I do, just design it for him?

Might actually be easier.

But you're correct, maybe I nudged Dave like I would an engineer, but
isn't this mild...

It is for someone who knows what you mean, but not for someone who
knows close to nothing. After all, the very first response was
confusion about "bias current." Well, if he doesn't know what it is
then he can't calculate it, right? And it's not because he can't
divide V by R. He didn't understand the jargon "bias current" and we
might as well ask him to calculate the fubar ratio. What's a fubar?

Worse, actually, because he was at least somewhat familiar with "bias
voltage" so instead of a completely alien term it seemed inconsistent
with the limited knowledge he did have..

[JT]

"Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

How much voltage gain do you need?

What is the load impedance? Is it a speaker?"

[Dave]

"Don't mean to be critical, but these seem like very generic"
questions."

==

What the hell does that mean?

I think it may have meant something akin to "how do those (generic)
things relate to my (specific) noisy speaker?"

Nothing like, "How...", or an answer to my gain question.

I certainly don't want to get into an 'argument' over this but you're
being rather 'selective' in the quotes. For "bias current" he tried to
'guess' you meant collector current (in the last stage) and answered
180 mA. As for gain, he figured he had enough. That, of course, isn't
what you asked but what difference does it make? (I imagine him
wondering since he probably didn't see that being related to his
stated 'problem'). He answered the speaker and load question: "Load is
an 8 Ohm speaker."

And after what you view as a mystery question he queried "What,
specifically, are you thinking?"

Now, I can see that, to you, the phrase "what are you thinking?" might
have sounded like a 'challenge' but I think he simply had no idea
where you were going, what the purpose of the 'calculations' were
(plus he didn't know what "bias current" meant), what the point was,
and how it related to his, not necessarily correct, concept of the
problem, which may not be the issues you were addressing.

Its not an uncommon problem when 'expert' speaks to 'novice' because
what is so engrained that it's instinctively 'knee jerk' obvious to
one, including the jargon, is 'huh?' to the other.

...Jim Thompson

Maybe it'd be easier if I simply design it for them. No controversy,
and maybe I gain a customer when they can't understand it O:-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Jim Thompson wrote:
"Don't mean to be critical, but these seem like very generic"
questions."

What the hell does that mean?

I think it may have meant something akin to "how do those (generic)
things relate to my (specific) noisy speaker?"

That showed a complete lack of common sense analytical ability. It isn't
just a lack of knowledge. He was being closed-minded.

I actually remember the first time I heard of bias current. It was upon
reading the datasheet for the LM319 comparator about 25 years ago. It took
about 100 ms to realize that, where there is a voltage applied to a finite
resistance, there is also a current, and it comes from the same source. The
reason Dave didn't realize that is not because it was too hard for him.
It's because he didn't know who you were, and assumed you didn't know what
you were talking about, so he didn't even think about it.

He might not know how to calculate Thevinin equivalents (that the parallel
resistance formula is applied to series resistors is not obvious) but he
didn't ask how. He just assumed you were wrong. Yes, he said it nicely at
first, but it was still an arrogant assumption.


--

Reply in group, but if emailing add one more
zero, and remove the last word.

On Fri, 08 Jun 2012 15:30:03 -0500, flipper wrote:

On Fri, 08 Jun 2012 09:31:33 -0700, Jim Thompson
wrote:

On Thu, 07 Jun 2012 23:38:42 -0500, flipper wrote:


Frankly, Jim, I think you've become so attuned to trading barbs with
'whoever' that the 'chip', so to speak, is on your shoulder and you
misinterpreted his lack of knowledge as 'smart mouthed'.

He said from day one he knows next to nothing so when you toss out
what are to you 'blindingly obvious' things like "bias current" he
doesn't know what you mean because, as he explained, 'to him' bias is
a voltage. That not being "smart mouthed," it's just all he knows from
what he's managed to 'pick up' from somewhere.

I suspect you're used to 'challenging' EEs to 'think' but that isn't
going to work here because he isn't an EE and will likely not
understand what you're asking. You need to 'explain' things to him,
not ask him to 'explain' it to you expecting that, in doing so, the
'light bulb' will go off and he'll 'realize' where you're going and
the thing he's overlooked.

So, what should I do, just design it for him?

Might actually be easier.

But you're correct, maybe I nudged Dave like I would an engineer, but
isn't this mild...

It is for someone who knows what you mean, but not for someone who
knows close to nothing. After all, the very first response was
confusion about "bias current." Well, if he doesn't know what it is
then he can't calculate it, right? And it's not because he can't
divide V by R. He didn't understand the jargon "bias current" and we
might as well ask him to calculate the fubar ratio. What's a fubar?

Worse, actually, because he was at least somewhat familiar with "bias
voltage" so instead of a completely alien term it seemed inconsistent
with the limited knowledge he did have..

[JT]

"Back up and do a little math. Calculate the bias current in that
last stage. (In fact, calculate all your stage biases.)

How much voltage gain do you need?

What is the load impedance? Is it a speaker?"

[Dave]

"Don't mean to be critical, but these seem like very generic"
questions."

==

What the hell does that mean?

I think it may have meant something akin to "how do those (generic)
things relate to my (specific) noisy speaker?"

Nothing like, "How...", or an answer to my gain question.

I certainly don't want to get into an 'argument' over this but you're
being rather 'selective' in the quotes. For "bias current" he tried to
'guess' you meant collector current (in the last stage) and answered
180 mA. As for gain, he figured he had enough. That, of course, isn't
what you asked but what difference does it make? (I imagine him
wondering since he probably didn't see that being related to his
stated 'problem'). He answered the speaker and load question: "Load is
an 8 Ohm speaker."

And after what you view as a mystery question he queried "What,
specifically, are you thinking?"

Now, I can see that, to you, the phrase "what are you thinking?" might
have sounded like a 'challenge' but I think he simply had no idea
where you were going, what the purpose of the 'calculations' were
(plus he didn't know what "bias current" meant), what the point was,
and how it related to his, not necessarily correct, concept of the
problem, which may not be the issues you were addressing.

Its not an uncommon problem when 'expert' speaks to 'novice' because
what is so engrained that it's instinctively 'knee jerk' obvious to
one, including the jargon, is 'huh?' to the other.

...Jim Thompson

BTW flipper this group is supposedly for working engineers. Persons like
Dave should stay in s.e.b instead.

?-)

"flipper" wrote in message
...
On Fri, 08 Jun 2012 22:03:13 -0700, josephkk
wrote:

BTW flipper this group is supposedly for working engineers.

Oh? That's the first I heard of it.

Persons like
Dave should stay in s.e.b instead.

Probably a good place to ask questions.

But let's give the boy some credit. He did post a schematic, which is
more on topic than a lot of what goes on around here.


And the person ripping on him was the worst offender.

On Wed, 23 May 2012 15:40:17 -0500, "Dave" wrote:

Posted a while back about a project I am trying to concoct- an intercom for
my front door- and have made some progress. Unfortunately I hit a speed
bump when I added transistor Q4. Now it only gives me noise at the output,
and lots and lots of that. Capacitors are all 100uF 35V, which I am
thinking may be the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it with a 2N5296
from my junkbox, but that just doubled the volume of the noisy output. If
anyone sees something I should but don't, please post. The only thing I can
think of is upping the voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave


See attachments showing bias and simulation. Googling suggests
intercom gain should be only 250X for speaker as source and speaker as
load. Plus the bias in that last stage is terminal.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Wed, 23 May 2012 15:40:17 -0500, "Dave" wrote:

Posted a while back about a project I am trying to concoct- an intercom for
my front door- and have made some progress. Unfortunately I hit a speed
bump when I added transistor Q4. Now it only gives me noise at the output,
and lots and lots of that. Capacitors are all 100uF 35V, which I am
thinking may be the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it with a 2N5296
from my junkbox, but that just doubled the volume of the noisy output. If
anyone sees something I should but don't, please post. The only thing I can
think of is upping the voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave


See...

From: Jim Thompson
Newsgroups: alt.binaries.schematics.electronic
Subject: Okay, so, what am I missing here?
Date: Fri, 08 Jun 2012 09:48:31 -0700
Message-ID:

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Wed, 23 May 2012 15:40:17 -0500, "Dave" wrote:

Posted a while back about a project I am trying to concoct- an intercom for
my front door- and have made some progress. Unfortunately I hit a speed
bump when I added transistor Q4. Now it only gives me noise at the output,
and lots and lots of that. Capacitors are all 100uF 35V, which I am
thinking may be the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it with a 2N5296
from my junkbox, but that just doubled the volume of the noisy output. If
anyone sees something I should but don't, please post. The only thing I can
think of is upping the voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave


See attachment for the KISS approach...

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Jim Thompson wrote:

See attachment for the KISS approach...

Why only 1 diode drop, and not 2, between the bases?

Or, why doesn't that cause non-linearity?


--

Reply in group, but if emailing add one more
zero, and remove the last word.

On Sat, 9 Jun 2012 19:43:57 -0400, "Tom Del Rosso"
wrote:


Jim Thompson wrote:

See attachment for the KISS approach...

Why only 1 diode drop, and not 2, between the bases?

2 Diodes runs the risk of thermal runaway... I was keeping it KISS.


Or, why doesn't that cause non-linearity?

Yes, But there's feedback, look at the waveform, you can see the
distortion, but it's mild... and it's just an intercom after all.

I CAN make the output PERFECT class-AB, but I will not be divulging
that technique... some day I hope to find a buyer... although that
hope keeps diminishing... the true audiophile seems long gone :-(

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Wed, 23 May 2012 15:40:17 -0500, "Dave" wrote:

Posted a while back about a project I am trying to concoct- an intercom for
my front door- and have made some progress. Unfortunately I hit a speed
bump when I added transistor Q4. Now it only gives me noise at the output,
and lots and lots of that. Capacitors are all 100uF 35V, which I am
thinking may be the problem (maybe the last couple need to be 50 or 75V?)
Originally thought I might be overdriving Q4, so I replaced it with a 2N5296
from my junkbox, but that just doubled the volume of the noisy output. If
anyone sees something I should but don't, please post. The only thing I can
think of is upping the voltage on C8 and C9.

Any help is *greatly* appreciated...

Dave


See attachments for bias and simulation results. Googling suggests
gain needed from a speaker source to a speaker load is only 250X. You
have too much gain, plus dissipation in last transistor would be
terminal.


...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

In article ,
josephkk wrote:

BTW flipper this group is supposedly for working engineers.

No, it isn't.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)