Just did a video DC restorer function (in CMOS) for a UTC camera chip,
and realized that it would be trivial to do the same function with
bipolar discrete devices.

On the S.E.D/Schematics page of my website check out...

Video_Restorer_Discrete_NPNs.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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 02/07/2014 20:36, Jim Thompson wrote:
Just did a video DC restorer function (in CMOS) for a UTC camera chip,
and realized that it would be trivial to do the same function with
bipolar discrete devices.

On the S.E.D/Schematics page of my website check out...

Video_Restorer_Discrete_NPNs.png

...Jim Thompson


I have used a similar idea before, but its general usefulness is limited
by the black level being dependent on the sync height, and to a small
extent, the average video level.

I'm surprised, given this video signal is of known origin, why would you
need such a circuit? Plus you can hardly integrate the 100nF on the CMOS.

--
Mike Perkins
Video Solutions Ltd
www.videosolutions.ltd.uk

On Wed, 02 Jul 2014 21:26:44 +0100, Mike Perkins
wrote:

On 02/07/2014 20:36, Jim Thompson wrote:
Just did a video DC restorer function (in CMOS) for a UTC camera chip,
and realized that it would be trivial to do the same function with
bipolar discrete devices.

On the S.E.D/Schematics page of my website check out...

Video_Restorer_Discrete_NPNs.png

...Jim Thompson


I have used a similar idea before, but its general usefulness is limited
by the black level being dependent on the sync height,

Everything is ratiometric in "IEEE Units". In my particular case the
video is fixed amplitude from sync tip to UTC (Coaxitron) peaks.

[UTC (Coaxitron) are the control bits for the camera.]

and to a small
extent, the average video level.

Wrong


I'm surprised, given this video signal is of known origin, why would you
need such a circuit? Plus you can hardly integrate the 100nF on the CMOS.

Video is commonly AC-coupled. A DC restorer "clamps" the sync tips to
ground, from which all measurements are referenced.

Who said the 100nF was integrated?

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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 a sunny day (Wed, 02 Jul 2014 21:26:44 +0100) it happened Mike Perkins
wrote in :

On 02/07/2014 20:36, Jim Thompson wrote:
Just did a video DC restorer function (in CMOS) for a UTC camera chip,
and realized that it would be trivial to do the same function with
bipolar discrete devices.

On the S.E.D/Schematics page of my website check out...

Video_Restorer_Discrete_NPNs.png

...Jim Thompson


I have used a similar idea before, but its general usefulness is limited
by the black level being dependent on the sync height, and to a small
extent, the average video level.


Right, the circuit is a DC resorter, but not a black level stabilizer.

A black level stabilizer will also restore DC level.
The black level stabilizer is *required* to keep the black level in the display device constant,
and usually all the way at the end of the 'chain' of amplifiers [1].
Sync amplitude changes, and cannot be used for that, and should not be dependent upon for display.

[1]
It is done by clamping at the black level, just after the sync,
and needs a special correctly timed pulse for that, as there is also the color burst there in a composite PAL or NTSC signal,
so it should be done where there is no burst, just before the CRT or whatever, and that is where you want the black level constant anyway.

You can make a good DC restorer by clamping on the sync tip to keep your signal in the linear amplifier range,
but that is ALL it is good for.
Not much accuracy is needed in such a case, as usually the amplifier range is much bigger than the composite signal,
so a simple diode will do in most cases.






I'm surprised,

I'm not :-)

On 02/07/2014 23:41, Jim Thompson wrote:
On Wed, 02 Jul 2014 21:26:44 +0100, Mike Perkins
wrote:

On 02/07/2014 20:36, Jim Thompson wrote:
Just did a video DC restorer function (in CMOS) for a UTC camera chip,
and realized that it would be trivial to do the same function with
bipolar discrete devices.

On the S.E.D/Schematics page of my website check out...

Video_Restorer_Discrete_NPNs.png

...Jim Thompson


I have used a similar idea before, but its general usefulness is limited
by the black level being dependent on the sync height,

Everything is ratiometric in "IEEE Units". In my particular case the
video is fixed amplitude from sync tip to UTC (Coaxitron) peaks.

[UTC (Coaxitron) are the control bits for the camera.]

and to a small
extent, the average video level.

Wrong

I see you have now removed the offending circuit from your website.

You "had" a 100k resistor down to ground to bias the circuit. The
current flowing through this, and the clamp will be dependent on video
level.
The clamp will have an impedance and so there will be a small variation
of clamp level with video level.

Ordinarily you would need a buffer after this to ensure the clamp is not
affected by anything downstream.



I'm surprised, given this video signal is of known origin, why would you
need such a circuit? Plus you can hardly integrate the 100nF on the CMOS.

Video is commonly AC-coupled. A DC restorer "clamps" the sync tips to
ground, from which all measurements are referenced.

Agreed, but why would your customer specifically introduce AC coupling?


Who said the 100nF was integrated?

...Jim Thompson


--
Mike Perkins
Video Solutions Ltd
www.videosolutions.ltd.uk

On 03/07/2014 07:33, Jan Panteltje wrote:
On a sunny day (Wed, 02 Jul 2014 21:26:44 +0100) it happened Mike Perkins
wrote in :

On 02/07/2014 20:36, Jim Thompson wrote:
Just did a video DC restorer function (in CMOS) for a UTC camera chip,
and realized that it would be trivial to do the same function with
bipolar discrete devices.

On the S.E.D/Schematics page of my website check out...

Video_Restorer_Discrete_NPNs.png

...Jim Thompson


I have used a similar idea before, but its general usefulness is limited
by the black level being dependent on the sync height, and to a small
extent, the average video level.


Right, the circuit is a DC resorter, but not a black level stabilizer.

A black level stabilizer will also restore DC level.
The black level stabilizer is *required* to keep the black level in the display device constant,
and usually all the way at the end of the 'chain' of amplifiers [1].
Sync amplitude changes, and cannot be used for that, and should not be dependent upon for display.

[1]
It is done by clamping at the black level, just after the sync,
and needs a special correctly timed pulse for that, as there is also the color burst there in a composite PAL or NTSC signal,
so it should be done where there is no burst, just before the CRT or whatever, and that is where you want the black level constant anyway.

Historically I would have used a parallel inductor and resistor to
ensure the burst is not significantly affected by a clamp.

You can make a good DC restorer by clamping on the sync tip to keep your signal in the linear amplifier range,
but that is ALL it is good for.
Not much accuracy is needed in such a case, as usually the amplifier range is much bigger than the composite signal,
so a simple diode will do in most cases.

Agreed, and I have also used a simple diode arrangement before. It all
depends on what you're trying to achieve.


I'm surprised,

I'm not :-)


--
Mike Perkins
Video Solutions Ltd
www.videosolutions.ltd.uk

On Thu, 03 Jul 2014 10:16:08 +0100, Mike Perkins
wrote:

On 02/07/2014 23:41, Jim Thompson wrote:
On Wed, 02 Jul 2014 21:26:44 +0100, Mike Perkins
wrote:

On 02/07/2014 20:36, Jim Thompson wrote:
Just did a video DC restorer function (in CMOS) for a UTC camera chip,
and realized that it would be trivial to do the same function with
bipolar discrete devices.

On the S.E.D/Schematics page of my website check out...

Video_Restorer_Discrete_NPNs.png

...Jim Thompson


I have used a similar idea before, but its general usefulness is limited
by the black level being dependent on the sync height,

Everything is ratiometric in "IEEE Units". In my particular case the
video is fixed amplitude from sync tip to UTC (Coaxitron) peaks.

[UTC (Coaxitron) are the control bits for the camera.]

and to a small
extent, the average video level.

Wrong

I see you have now removed the offending circuit from your website.

Huh? It's still there.


You "had" a 100k resistor down to ground to bias the circuit. The
current flowing through this, and the clamp will be dependent on video
level.
The clamp will have an impedance and so there will be a small variation
of clamp level with video level.

Careful there, sonny. You're displaying your ignorance of circuit
design.


Ordinarily you would need a buffer after this to ensure the clamp is not
affected by anything downstream.

I live in a hi-Z world... it's called CMOS. But it's not hard to have
a "downstream" bipolar comparator to do the UTC slicing and NOT load
the clamp.




I'm surprised, given this video signal is of known origin, why would you
need such a circuit? Plus you can hardly integrate the 100nF on the CMOS.

Video is commonly AC-coupled. A DC restorer "clamps" the sync tips to
ground, from which all measurements are referenced.

Agreed, but why would your customer specifically introduce AC coupling?

Why do you have a hair up your butt?



Who said the 100nF was integrated?

...Jim Thompson


...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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 03/07/2014 15:19, Jim Thompson wrote:
On Thu, 03 Jul 2014 10:16:08 +0100, Mike Perkins
wrote:

On 02/07/2014 23:41, Jim Thompson wrote:
On Wed, 02 Jul 2014 21:26:44 +0100, Mike Perkins
wrote:

On 02/07/2014 20:36, Jim Thompson wrote:
Just did a video DC restorer function (in CMOS) for a UTC camera chip,
and realized that it would be trivial to do the same function with
bipolar discrete devices.

On the S.E.D/Schematics page of my website check out...

Video_Restorer_Discrete_NPNs.png

...Jim Thompson


I have used a similar idea before, but its general usefulness is limited
by the black level being dependent on the sync height,

Everything is ratiometric in "IEEE Units". In my particular case the
video is fixed amplitude from sync tip to UTC (Coaxitron) peaks.

[UTC (Coaxitron) are the control bits for the camera.]

and to a small
extent, the average video level.

Wrong

I see you have now removed the offending circuit from your website.

Huh? It's still there.

Yes - forgot it was in a lower directory.


You "had" a 100k resistor down to ground to bias the circuit. The
current flowing through this, and the clamp will be dependent on video
level.
The clamp will have an impedance and so there will be a small variation
of clamp level with video level.

Careful there, sonny. You're displaying your ignorance of circuit
design.

It depends on what you want to do. If you want a crude video restore
then fewer components could be used.


Ordinarily you would need a buffer after this to ensure the clamp is not
affected by anything downstream.

I live in a hi-Z world... it's called CMOS. But it's not hard to have
a "downstream" bipolar comparator to do the UTC slicing and NOT load
the clamp.

Most things have to interface to the real world and composite video is
generally associated with 75 ohm impedance.



I'm surprised, given this video signal is of known origin, why would you
need such a circuit? Plus you can hardly integrate the 100nF on the CMOS.

Video is commonly AC-coupled. A DC restorer "clamps" the sync tips to
ground, from which all measurements are referenced.

Agreed, but why would your customer specifically introduce AC coupling?

Why do you have a hair up your butt?

Is your abuse to cover being unable to answer a very simple question.

Most CMOS and integrated camera provide a DC output with no real need
for DC restoration. Very old ones, yes.

At most a DC shift in output is all that would be needed, and that
doesn't cause complications like line droop.



Who said the 100nF was integrated?

...Jim Thompson


...Jim Thompson


--
Mike Perkins
Video Solutions Ltd
www.videosolutions.ltd.uk

On Thu, 03 Jul 2014 17:14:15 +0100, Mike Perkins
wrote:

On 03/07/2014 15:19, Jim Thompson wrote:
On Thu, 03 Jul 2014 10:16:08 +0100, Mike Perkins
wrote:

On 02/07/2014 23:41, Jim Thompson wrote:
On Wed, 02 Jul 2014 21:26:44 +0100, Mike Perkins
wrote:

On 02/07/2014 20:36, Jim Thompson wrote:
Just did a video DC restorer function (in CMOS) for a UTC camera chip,
and realized that it would be trivial to do the same function with
bipolar discrete devices.

On the S.E.D/Schematics page of my website check out...

Video_Restorer_Discrete_NPNs.png

...Jim Thompson


I have used a similar idea before, but its general usefulness is limited
by the black level being dependent on the sync height,

Everything is ratiometric in "IEEE Units". In my particular case the
video is fixed amplitude from sync tip to UTC (Coaxitron) peaks.

[UTC (Coaxitron) are the control bits for the camera.]

and to a small
extent, the average video level.

Wrong

I see you have now removed the offending circuit from your website.

Huh? It's still there.

Yes - forgot it was in a lower directory.


You "had" a 100k resistor down to ground to bias the circuit. The
current flowing through this, and the clamp will be dependent on video
level.
The clamp will have an impedance and so there will be a small variation
of clamp level with video level.

Careful there, sonny. You're displaying your ignorance of circuit
design.

It depends on what you want to do. If you want a crude video restore
then fewer components could be used.


Ordinarily you would need a buffer after this to ensure the clamp is not
affected by anything downstream.

I live in a hi-Z world... it's called CMOS. But it's not hard to have
a "downstream" bipolar comparator to do the UTC slicing and NOT load
the clamp.

Most things have to interface to the real world and composite video is
generally associated with 75 ohm impedance.

This hangs "to the side" and does not pass on anything other than
voltages to hi-Z measuring/decoding equipment.




I'm surprised, given this video signal is of known origin, why would you
need such a circuit? Plus you can hardly integrate the 100nF on the CMOS.

Video is commonly AC-coupled. A DC restorer "clamps" the sync tips to
ground, from which all measurements are referenced.

Agreed, but why would your customer specifically introduce AC coupling?

Why do you have a hair up your butt?

Is your abuse to cover being unable to answer a very simple question.

Nope. I just think you're struggling to be a horse's ass.


Most CMOS and integrated camera provide a DC output with no real need
for DC restoration. Very old ones, yes.

What can I say... my customer makes chips for the security and
surveillance camera business. His customers want this function. I
aims to please ;-)

And I have Sony circuit examples that do the same functions... my
customer's competition. So I do form/fit/function differently enough
to be patentable.


At most a DC shift in output is all that would be needed, and that
doesn't cause complications like line droop.

You're totally misunderstanding the function.

[snip]

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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, 02 Jul 2014 12:36:11 -0700, Jim Thompson
wrote:

Just did a video DC restorer function (in CMOS) for a UTC camera chip,
and realized that it would be trivial to do the same function with
bipolar discrete devices.

On the S.E.D/Schematics page of my website check out...

Video_Restorer_Discrete_NPNs.png

...Jim Thompson

Updated to...

Video_Restorer_Discrete_NPNs.pdf

to show input impedance/(near)ideal-diode behavior.

[Aside: Does anyone know if you can make 2+ pages as PNG's?]

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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, 03 Jul 2014 10:47:42 -0700, Jim Thompson
wrote:

[Aside: Does anyone know if you can make 2+ pages as PNG's?]

Not sure exactly what you want, but a PNG is just an image
file... it can be any size you like.

I just recently scanned a 2-page article, saving each page
as a separate PNG. Then fired up GIMP (Windows Paint would
work as well) opened Page 2, selected All, copied to
clipboard, opened Page 1, doubled the height of the work
area, and pasted Page 2 at the bottom. Worked great, and
was about 1/4 the file size of a PDF (but that may have been
due to the cheesy free PDF converter I tested against).

You could paste the second page next to the first instead of
below it, if you needed that for some reason.

Best regards,


Bob Masta

DAQARTA v7.60
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