Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

http://www.datasheetarchive.com/2--PF5301-2-datasheet.html
Not exactly a data sheet, but it does have some specs. There should
be some other acceptable devices in the chart. 2N4117A or 2N4118 look
very close.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?


--

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 Fri, 28 Jun 2013 06:51:11 -0700 John Larkin
wrote in Message id:
:

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Thanks.

On Fri, 28 Jun 2013 06:08:55 -0700 Jeff Liebermann
wrote in Message id: :

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

http://www.datasheetarchive.com/2--PF5301-2-datasheet.html
Not exactly a data sheet, but it does have some specs. There should
be some other acceptable devices in the chart. 2N4117A or 2N4118 look
very close.

ITYM PN4117A and PN4118A. [Google] Or maybe so?

Those do look good and there seems to be some out there, but I'm not too
crazy about sources that ask for a RFQ only to tell you that they have a
$100 minimum. Was hoping for something I could buy at Digikey or Mouser or
some other distributor with no minimums.

Although there is a Vishay 2N4117A-E3
http://www.mouser.com/ProductDetail/...39y4wHUM%3d I
I wonder what the -E3 means? I found a datasheet, but it does not state
what -E3 is.

Vishay also has a 2N4118A.
http://www.mouser.com/ProductDetail/...dZHJqghFYzA%3d
In stock too. Maybe I'll give that one a go, wrong package but beggars
can't be choosers.

A pity that these are all EOL. *sigh*

Thanks, Jeff.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Hmmm... Would that -- or a similar -- op-amp be suitable?

On Fri, 28 Jun 2013 10:51:41 -0400, JW wrote:

On Fri, 28 Jun 2013 06:08:55 -0700 Jeff Liebermann
wrote in Message id: :

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

http://www.datasheetarchive.com/2--PF5301-2-datasheet.html
Not exactly a data sheet, but it does have some specs. There should
be some other acceptable devices in the chart. 2N4117A or 2N4118 look
very close.

ITYM PN4117A and PN4118A. [Google] Or maybe so?

Actually, they look very much like the PF5301 with a JEDEC registered
number instead of a NS only number.

Those do look good and there seems to be some out there, but I'm not too
crazy about sources that ask for a RFQ only to tell you that they have a
$100 minimum. Was hoping for something I could buy at Digikey or Mouser or
some other distributor with no minimums.

Welcome to eBay, my favorite source for all things odd and
unobtainable.
www.ebay.com/sch/i.html?_nkw=2n4117
www.ebay.com/sch/i.html?_nkw=2n4118
I suggest you buy from two different US vendors and get some spares.
Don't be surprised if you get unarked parts stolen off the production
line, fished out of the rejects bin, or are counterfeits (especially
electrolytics). For eBay parts, you can have anything you want except
quality. Q302 is not part of a differential pair, so you shouldn't
need to do any matching. Good luck.

A pity that these are all EOL. *sigh*

I'm getting old enough to be declared EOL. No sympathy.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Fri, 28 Jun 2013 10:33:35 -0400, JW wrote:

On Fri, 28 Jun 2013 06:51:11 -0700 John Larkin
wrote in Message id:
:

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Thanks.

Yikes, it's a jfet darlington! Really a weird circuit, overall.

I bet a 2N7000 would work. It's just an AC amplifier. Gate currents on a 2N7000
are femtoamps. You can turn one halfway on and leave the gate open, and it will
stay halfway on for hours. Fun to play with.

https://dl.dropboxusercontent.com/u/...rts/2N7000.jpg




--

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

JW schrieb:
Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. ...

Hi,

I could send you photos (don't have access to a scanner till Monday):
interested? If yes, just contact me per PM.

CU

Reinhard

On Fri, 28 Jun 2013 08:44:57 -0700, John Larkin
wrote:

On Fri, 28 Jun 2013 10:33:35 -0400, JW wrote:

On Fri, 28 Jun 2013 06:51:11 -0700 John Larkin
wrote in Message id:
:

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Thanks.

Yikes, it's a jfet darlington! Really a weird circuit, overall.

I bet a 2N7000 would work. It's just an AC amplifier. Gate currents on a 2N7000
are femtoamps. You can turn one halfway on and leave the gate open, and it will
stay halfway on for hours. Fun to play with.

https://dl.dropboxusercontent.com/u/...rts/2N7000.jpg


Hmmm, biasing might be tricky. It might be better to replace both jfets with one
2N7000.

Q302 has a lot of drain-source voltage. I'm wondering why it doesn't have a lot
of gate current.


--

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 06/28/2013 05:44 PM, John Larkin wrote:
On Fri, 28 Jun 2013 10:33:35 -0400, JW wrote:

On Fri, 28 Jun 2013 06:51:11 -0700 John Larkin
wrote in Message id:
:

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Thanks.

Yikes, it's a jfet darlington! Really a weird circuit, overall.

I bet a 2N7000 would work. It's just an AC amplifier. Gate currents on a 2N7000
are femtoamps. You can turn one halfway on and leave the gate open, and it will
stay halfway on for hours. Fun to play with.

Did you get the fA figure by measurements? The Onsemi and the Fairchild
give 10 nA as the leakage value. Guess they are much better than
specified...

Pere


https://dl.dropboxusercontent.com/u/...rts/2N7000.jpg

JW wrote:
Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.


How about this?

http://www.trendsetter.com/v/vspfile...40,%20U441.pdf

Around $8 but there's two in the package.

--
Regards, Joerg

http://www.analogconsultants.com/

o pere o writes:

On 06/28/2013 05:44 PM, John Larkin wrote:
On Fri, 28 Jun 2013 10:33:35 -0400, JW wrote:

On Fri, 28 Jun 2013 06:51:11 -0700 John Larkin
wrote in Message id:
:

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Thanks.

Yikes, it's a jfet darlington! Really a weird circuit, overall.

I bet a 2N7000 would work. It's just an AC amplifier. Gate currents on a 2N7000
are femtoamps. You can turn one halfway on and leave the gate open, and it will
stay halfway on for hours. Fun to play with.

Did you get the fA figure by measurements? The Onsemi and the
Fairchild give 10 nA as the leakage value. Guess they are much better
than specified...

I expect they can't be bothered to test them; it would take too long to
resolve fA I think. But 10nA is huge.

[...]


--

John Devereux

A pity that these are all EOL. *sigh*

I managed to purchase a few dozen PN4117A (new-old-stock Calogic) on
eBay last year... figured they might be useful for playing around with
ion-chamber radiation detector designs. There are still a couple of
vendors on eBay offering these.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Fri, 28 Jun 2013 19:39:31 +0200, o pere o wrote:

On 06/28/2013 05:44 PM, John Larkin wrote:
On Fri, 28 Jun 2013 10:33:35 -0400, JW wrote:

On Fri, 28 Jun 2013 06:51:11 -0700 John Larkin
wrote in Message id:
:

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Thanks.

Yikes, it's a jfet darlington! Really a weird circuit, overall.

I bet a 2N7000 would work. It's just an AC amplifier. Gate currents on a 2N7000
are femtoamps. You can turn one halfway on and leave the gate open, and it will
stay halfway on for hours. Fun to play with.

Did you get the fA figure by measurements? The Onsemi and the Fairchild
give 10 nA as the leakage value. Guess they are much better than
specified...

Pere


Yes, by experimenting. Leakage seems to be modest numbers of electrons
per second. That would be hard to production test, on a 3 cent part.




--

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

In article ,
o pere o writes:

Did you get the fA figure by measurements? The Onsemi and the Fairchild
give 10 nA as the leakage value. Guess they are much better than
specified...

If it's speced at 10 nA at max temperature,
what would you expect at room temp?


--
These are my opinions. I hate spam.

On 6/28/2013 12:34 PM, John Larkin wrote:
On Fri, 28 Jun 2013 08:44:57 -0700, John Larkin
wrote:

On Fri, 28 Jun 2013 10:33:35 -0400, JW wrote:

On Fri, 28 Jun 2013 06:51:11 -0700 John Larkin
wrote in Message id:
:

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Thanks.

Yikes, it's a jfet darlington! Really a weird circuit, overall.

I bet a 2N7000 would work. It's just an AC amplifier. Gate currents on a 2N7000
are femtoamps. You can turn one halfway on and leave the gate open, and it will
stay halfway on for hours. Fun to play with.

https://dl.dropboxusercontent.com/u/...rts/2N7000.jpg


Hmmm, biasing might be tricky. It might be better to replace both jfets with one
2N7000.

Q302 has a lot of drain-source voltage. I'm wondering why it doesn't have a lot
of gate current.


Maybe it's a cascode internally?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510 USA
+1 845 480 2058

hobbs at electrooptical dot net
http://electrooptical.net

On Fri, 28 Jun 2013 20:02:29 -0400, Phil Hobbs
wrote:

On 6/28/2013 12:34 PM, John Larkin wrote:
On Fri, 28 Jun 2013 08:44:57 -0700, John Larkin
wrote:

On Fri, 28 Jun 2013 10:33:35 -0400, JW wrote:

On Fri, 28 Jun 2013 06:51:11 -0700 John Larkin
wrote in Message id:
:

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Thanks.

Yikes, it's a jfet darlington! Really a weird circuit, overall.

I bet a 2N7000 would work. It's just an AC amplifier. Gate currents on a 2N7000
are femtoamps. You can turn one halfway on and leave the gate open, and it will
stay halfway on for hours. Fun to play with.

https://dl.dropboxusercontent.com/u/...rts/2N7000.jpg


Hmmm, biasing might be tricky. It might be better to replace both jfets with one
2N7000.

Q302 has a lot of drain-source voltage. I'm wondering why it doesn't have a lot
of gate current.


Maybe it's a cascode internally?

Cheers

Phil Hobbs

Was there such a thing, a 3-pin jfet cascode? There were some cute
dual-gate gaasfets that worked great as sorta-cascodes.

I only recently discovered the jfet impact ionization gate current
thing, while working on one of your circuits actually. See AoE p 136.


--

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 6/28/2013 8:13 PM, John Larkin wrote:
On Fri, 28 Jun 2013 20:02:29 -0400, Phil Hobbs
wrote:

On 6/28/2013 12:34 PM, John Larkin wrote:
On Fri, 28 Jun 2013 08:44:57 -0700, John Larkin
wrote:

On Fri, 28 Jun 2013 10:33:35 -0400, JW wrote:

On Fri, 28 Jun 2013 06:51:11 -0700 John Larkin
wrote in Message id:
:

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Thanks.

Yikes, it's a jfet darlington! Really a weird circuit, overall.

I bet a 2N7000 would work. It's just an AC amplifier. Gate currents on a 2N7000
are femtoamps. You can turn one halfway on and leave the gate open, and it will
stay halfway on for hours. Fun to play with.

https://dl.dropboxusercontent.com/u/...rts/2N7000.jpg


Hmmm, biasing might be tricky. It might be better to replace both jfets with one
2N7000.

Q302 has a lot of drain-source voltage. I'm wondering why it doesn't have a lot
of gate current.


Maybe it's a cascode internally?

Cheers

Phil Hobbs

Was there such a thing, a 3-pin jfet cascode? There were some cute
dual-gate gaasfets that worked great as sorta-cascodes.

I only recently discovered the jfet impact ionization gate current
thing, while working on one of your circuits actually. See AoE p 136.

Yup, I remember learning about it there. It really only happens with
N-channel devices, and only at V_DS above about 5V.

I recall some old National app notes referencing an integrated JFET
cascode, but they're at the lab and I'm at home. Older datasheets and
app notes on the web have been becoming inaccessible alarmingly fast
lately, due to all the parasites. Hang on to those old National Linear
Applications books, guys!

On another topic We're having a barbecue tomorrow, so I just picked up a
couple of torpedo kegs from Captain Lawrence, a first rate local
brewery. Their stuff is amazing, especially "Liquid Gold", which is a
clove-scented ale, and "Imperial IPA", which is nice and hoppy without
being one-dimensional like Dogfish.

If we can pry you and Mo off the Left Coast sometime, we'll take you to
their tasting room. (Picture a Napa Valley tasting room on the New
Jersey Turnpike, and you get the idea. Mindbending.)

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510 USA
+1 845 480 2058

hobbs at electrooptical dot net
http://electrooptical.net

Phil Hobbs wrote:

I recall some old National app notes referencing an integrated JFET
cascode, but they're at the lab and I'm at home. Older datasheets and
app notes on the web have been becoming inaccessible alarmingly fast
lately, due to all the parasites. Hang on to those old National Linear
Applications books, guys!


You might find some he


https://docs.google.com/folder/d/0B7w5p5pSKM5gc1VrTjBuOFZIX1U/edit?docId=0B7w5p5pSKM5ga0IxT1FubkdoanM

Phil Hobbs wrote:

On 6/28/2013 8:13 PM, John Larkin wrote:
On Fri, 28 Jun 2013 20:02:29 -0400, Phil Hobbs
wrote:

On 6/28/2013 12:34 PM, John Larkin wrote:
On Fri, 28 Jun 2013 08:44:57 -0700, John Larkin
wrote:

On Fri, 28 Jun 2013 10:33:35 -0400, JW wrote:

On Fri, 28 Jun 2013 06:51:11 -0700 John Larkin
wrote in Message id:
:

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Thanks.

Yikes, it's a jfet darlington! Really a weird circuit, overall.

I bet a 2N7000 would work. It's just an AC amplifier. Gate currents on a 2N7000
are femtoamps. You can turn one halfway on and leave the gate open, and it will
stay halfway on for hours. Fun to play with.

https://dl.dropboxusercontent.com/u/...rts/2N7000.jpg


Hmmm, biasing might be tricky. It might be better to replace both jfets with one
2N7000.

Q302 has a lot of drain-source voltage. I'm wondering why it doesn't have a lot
of gate current.


Maybe it's a cascode internally?

Cheers

Phil Hobbs

Was there such a thing, a 3-pin jfet cascode? There were some cute
dual-gate gaasfets that worked great as sorta-cascodes.

I only recently discovered the jfet impact ionization gate current
thing, while working on one of your circuits actually. See AoE p 136.

Yup, I remember learning about it there. It really only happens with
N-channel devices, and only at V_DS above about 5V.

I recall some old National app notes referencing an integrated JFET
cascode, but they're at the lab and I'm at home. Older datasheets and
app notes on the web have been becoming inaccessible alarmingly fast
lately, due to all the parasites. Hang on to those old National Linear
Applications books, guys!

On another topic We're having a barbecue tomorrow, so I just picked up a
couple of torpedo kegs from Captain Lawrence, a first rate local
brewery. Their stuff is amazing, especially "Liquid Gold", which is a
clove-scented ale, and "Imperial IPA", which is nice and hoppy without
being one-dimensional like Dogfish.

If we can pry you and Mo off the Left Coast sometime, we'll take you to
their tasting room. (Picture a Napa Valley tasting room on the New
Jersey Turnpike, and you get the idea. Mindbending.)


Found it. National NDF9401 through NDF9410 monolithic JFET cascodes.
The text of the National 1977 FET databook is on archive.org (no images
unfortunately).

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510 USA
+1 845 480 2058

hobbs at electrooptical dot net
http://electrooptical.net

On 6/28/2013 8:52 PM, Michael A. Terrell wrote:

Phil Hobbs wrote:

I recall some old National app notes referencing an integrated JFET
cascode, but they're at the lab and I'm at home. Older datasheets and
app notes on the web have been becoming inaccessible alarmingly fast
lately, due to all the parasites. Hang on to those old National Linear
Applications books, guys!


You might find some he


https://docs.google.com/folder/d/0B7w5p5pSKM5gc1VrTjBuOFZIX1U/edit?docId=0B7w5p5pSKM5ga0IxT1FubkdoanM

Glorious, thanks.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510 USA
+1 845 480 2058

hobbs at electrooptical dot net
http://electrooptical.net

On 2013-06-29, Phil Hobbs wrote:
Phil Hobbs wrote:

On 6/28/2013 8:13 PM, John Larkin wrote:
On Fri, 28 Jun 2013 20:02:29 -0400, Phil Hobbs
wrote:

On 6/28/2013 12:34 PM, John Larkin wrote:
On Fri, 28 Jun 2013 08:44:57 -0700, John Larkin
wrote:

On Fri, 28 Jun 2013 10:33:35 -0400, JW wrote:

On Fri, 28 Jun 2013 06:51:11 -0700 John Larkin
wrote in Message id:
:

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Thanks.

Yikes, it's a jfet darlington! Really a weird circuit, overall.

I bet a 2N7000 would work. It's just an AC amplifier. Gate currents on a 2N7000
are femtoamps. You can turn one halfway on and leave the gate open, and it will
stay halfway on for hours. Fun to play with.

https://dl.dropboxusercontent.com/u/...rts/2N7000.jpg


Hmmm, biasing might be tricky. It might be better to replace both jfets with one
2N7000.

Q302 has a lot of drain-source voltage. I'm wondering why it doesn't have a lot
of gate current.


Maybe it's a cascode internally?

Cheers

Phil Hobbs

Was there such a thing, a 3-pin jfet cascode? There were some cute
dual-gate gaasfets that worked great as sorta-cascodes.

I only recently discovered the jfet impact ionization gate current
thing, while working on one of your circuits actually. See AoE p 136.

Yup, I remember learning about it there. It really only happens with
N-channel devices, and only at V_DS above about 5V.

I recall some old National app notes referencing an integrated JFET
cascode, but they're at the lab and I'm at home. Older datasheets and
app notes on the web have been becoming inaccessible alarmingly fast
lately, due to all the parasites. Hang on to those old National Linear
Applications books, guys!

On another topic We're having a barbecue tomorrow, so I just picked up a
couple of torpedo kegs from Captain Lawrence, a first rate local
brewery. Their stuff is amazing, especially "Liquid Gold", which is a
clove-scented ale, and "Imperial IPA", which is nice and hoppy without
being one-dimensional like Dogfish.

If we can pry you and Mo off the Left Coast sometime, we'll take you to
their tasting room. (Picture a Napa Valley tasting room on the New
Jersey Turnpike, and you get the idea. Mindbending.)


Found it. National NDF9401 through NDF9410 monolithic JFET cascodes.
The text of the National 1977 FET databook is on archive.org (no images
unfortunately).

Hmm, JFET, so depletion; it was probably like this.

|
|
|--'
|
.---|--.
| |
| |
| |--'
| |
----|---|--.
| |
`-------+
|
|

JFET cascode

--
š‚šƒ 100% natural

--- news://freenews.netfront.net/ - complaints: ---

On 2013-06-29, Jasen Betts wrote:

Hmm, JFET, so depletion; it was probably like this.

Gah! I forgot how to draw fets


--
š‚šƒ 100% natural

Phil Hobbs wrote:

On 6/28/2013 8:52 PM, Michael A. Terrell wrote:

Phil Hobbs wrote:

I recall some old National app notes referencing an integrated JFET
cascode, but they're at the lab and I'm at home. Older datasheets and
app notes on the web have been becoming inaccessible alarmingly fast
lately, due to all the parasites. Hang on to those old National Linear
Applications books, guys!


You might find some he


https://docs.google.com/folder/d/0B7w5p5pSKM5gc1VrTjBuOFZIX1U/edit?docId=0B7w5p5pSKM5ga0IxT1FubkdoanM

Glorious, thanks.


Some other links you might find useful:

http://www.davmar.org/concepts.html

https://docs.google.com/folder/d/0B7...hhOGZUQ1E/edit

https://docs.google.com/folder/d/0B7...UgzdmlSMTdJREU

http://manoman.sqhill.com/books.php

http://manoman.sqhill.com/hp.php

http://manoman.sqhill.com/tek.php

http://w140.com/tekwiki/wiki/Main_Page#Carts

http://www.excesssolutions.com/cgi-bin/item/ES4139

http://www.excesssolutions.com/cgi-bin/item/ES5112

On 6/29/2013 4:02 AM, Jasen Betts wrote:
On 2013-06-29, Phil Hobbs wrote:
Phil Hobbs wrote:

On 6/28/2013 8:13 PM, John Larkin wrote:
On Fri, 28 Jun 2013 20:02:29 -0400, Phil Hobbs
wrote:

On 6/28/2013 12:34 PM, John Larkin wrote:
On Fri, 28 Jun 2013 08:44:57 -0700, John Larkin
wrote:

On Fri, 28 Jun 2013 10:33:35 -0400, JW wrote:

On Fri, 28 Jun 2013 06:51:11 -0700 John Larkin
wrote in Message id:
:

On Fri, 28 Jun 2013 08:45:19 -0400, JW wrote:

Looking for a suitable cross-reference for a National PF5301 TO-92 N
channel JFET as I can't find the original part anywhere. Hell, I can't
even find an original datasheet. The critical parameter for the sub is
Igss which for the National part is 1pA. The only thing I've been able to
find so far is a Linear Systems LS5301 which has a Ig of 1pA, but at $40 a
pop (!), I'd like to find an alternate.

Does anyone know of any possible substitutes?

Thanks.

What's the application? Do you really need a jfet?

I'm pretty sure I do, as it looks to be a fairly sensitive circuit. It's
for a repair on a Keithley 220 programmable current source.
http://www.google.com/url?sa=t&rct=j...eEEYYk4sluspuA

The schematic is on page 6-31/6-32 (4 pages from the end) location Q302
near the top of the page. It's part of circuit which uses a AD515K
FET-Input Electrometer Op-amp.

Thanks.

Yikes, it's a jfet darlington! Really a weird circuit, overall.

I bet a 2N7000 would work. It's just an AC amplifier. Gate currents on a 2N7000
are femtoamps. You can turn one halfway on and leave the gate open, and it will
stay halfway on for hours. Fun to play with.

https://dl.dropboxusercontent.com/u/...rts/2N7000.jpg


Hmmm, biasing might be tricky. It might be better to replace both jfets with one
2N7000.

Q302 has a lot of drain-source voltage. I'm wondering why it doesn't have a lot
of gate current.


Maybe it's a cascode internally?

Cheers

Phil Hobbs

Was there such a thing, a 3-pin jfet cascode? There were some cute
dual-gate gaasfets that worked great as sorta-cascodes.

I only recently discovered the jfet impact ionization gate current
thing, while working on one of your circuits actually. See AoE p 136.

Yup, I remember learning about it there. It really only happens with
N-channel devices, and only at V_DS above about 5V.

I recall some old National app notes referencing an integrated JFET
cascode, but they're at the lab and I'm at home. Older datasheets and
app notes on the web have been becoming inaccessible alarmingly fast
lately, due to all the parasites. Hang on to those old National Linear
Applications books, guys!

On another topic We're having a barbecue tomorrow, so I just picked up a
couple of torpedo kegs from Captain Lawrence, a first rate local
brewery. Their stuff is amazing, especially "Liquid Gold", which is a
clove-scented ale, and "Imperial IPA", which is nice and hoppy without
being one-dimensional like Dogfish.

If we can pry you and Mo off the Left Coast sometime, we'll take you to
their tasting room. (Picture a Napa Valley tasting room on the New
Jersey Turnpike, and you get the idea. Mindbending.)


Found it. National NDF9401 through NDF9410 monolithic JFET cascodes.
The text of the National 1977 FET databook is on archive.org (no images
unfortunately).

Hmm, JFET, so depletion; it was probably like this.

|
|
|--'
|
.---|--.
| |
| |
| |--'
| |
----|---|--.
| |
`-------+
|
|

JFET cascode


Right. The top FET takes all the impact ionization gate current and
shunts it to the source. The bottom one runs at some nearly constant
~2ish volts V_DS.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510 USA
+1 845 480 2058

hobbs at electrooptical dot net
http://electrooptical.net