A sample hold circuit

[didibabawu]

pic sample hold

In the picture is a sample hold circuit of pipeline ADC. Maybe most people use only the left part. But I have seen from a famous company's schematic that they use an amplifier to control the common mode voltage of the SHA input.
So, I want to know why the feed back circuit was used?

 

[sec]

maybe I am totally wrong, but it seems to me look like a switched capacitor filter ... just saying that, maybe it will help

 

[didibabawu]

There is something missing in the previous picture, I have changed the new one.

 

[waxtomato]

I find some of this kind of circuit in S/H with CDS& AMP for readout diff signal (MIcron imager)

 

[didibabawu]

I find some of this kind of circuit in S/H with CDS& AMP for readout diff signal (MIcron imager)

Do you know why using the amp in the right?

 

[panditabupesh]

Hello
That famous company has a patent and a jssc paper, I think Nov 1996, on it- I suggest going through them.

Bupesh

 

[zouyufeng]

common feed back : 1)continuous
2)discrete

picture you give is 1)

 

[panditabupesh]

Sorry I gave the wrong reference, memory plays tricks some times, the actual reference is:

A single-ended 12-bit 20 Msample/s self-calibrating pipeline A/D converter
Opris, I.E.; Lewicki, L.D.; Wong, B.C.;
Solid-State Circuits, IEEE Journal of
Volume 33, Issue 12, Dec. 1998 Page(s):1898 - 1903

Hope it helps

Bupesh