thomasross20
Newbie level 3
Hi all,
I'm building a pipeline ADC... usually in the sampling phase, the amplifier is tied in unity-gain configuration. However, I'm using a fully-differential telescopic amplifier with output cmomon mode = 1.3V and input common mode = 0.9V... I've searched the literature but cannot find a thing relating to what the amp is to do when the caps are sampling.... it can't be put into unity gain as normal. I use SC-CMFB which tried to keep the output at 1.3V during the sampling, but right now the amplifier is open-loop during sampling, which is not ideal... any hints?
I've also found little literature on the topic of amp measurments when using an amp which different input and output common modes. What I do for gain/phase is the usual resistor and cap round the feedback to set up d.c. but block a.c. - though of course there is a little current flowing through the resistor due to the difference in common-mode levels - I don't think this is too much of a problem? Anyway, thanks for any help!
I'm building a pipeline ADC... usually in the sampling phase, the amplifier is tied in unity-gain configuration. However, I'm using a fully-differential telescopic amplifier with output cmomon mode = 1.3V and input common mode = 0.9V... I've searched the literature but cannot find a thing relating to what the amp is to do when the caps are sampling.... it can't be put into unity gain as normal. I use SC-CMFB which tried to keep the output at 1.3V during the sampling, but right now the amplifier is open-loop during sampling, which is not ideal... any hints?
I've also found little literature on the topic of amp measurments when using an amp which different input and output common modes. What I do for gain/phase is the usual resistor and cap round the feedback to set up d.c. but block a.c. - though of course there is a little current flowing through the resistor due to the difference in common-mode levels - I don't think this is too much of a problem? Anyway, thanks for any help!