jrom
Newbie level 4
Dear reader,
This is my first post. If I did something wrong, please let me know.
I am trying to design a folded cascode opamp that will be integrated in a sensor read-out design. I need to use a differential amplifier topology. The implementation will be fabricated, as it is part of my graduation assignment. The software I use is Cadence Virtuoso.
My problem is such: My simulation results tell me that I can achieve pretty decent open loop gain (about 60x, so 35dB), however, when I close the loop for unity gain the closed loop gain is not as expected. And with that I mean: either a very small output signal, or simply a DC signal when it should be AC. I have already tried a lot, but so far not a single time the closed loop worked.
I included a picture of my schematic. I suspect that I made a simple and trivial mistake. Or my biasing is incorrect.
The schematic (closed loop):
Thank you in advance,
Joost
This is my first post. If I did something wrong, please let me know.
I am trying to design a folded cascode opamp that will be integrated in a sensor read-out design. I need to use a differential amplifier topology. The implementation will be fabricated, as it is part of my graduation assignment. The software I use is Cadence Virtuoso.
My problem is such: My simulation results tell me that I can achieve pretty decent open loop gain (about 60x, so 35dB), however, when I close the loop for unity gain the closed loop gain is not as expected. And with that I mean: either a very small output signal, or simply a DC signal when it should be AC. I have already tried a lot, but so far not a single time the closed loop worked.
I included a picture of my schematic. I suspect that I made a simple and trivial mistake. Or my biasing is incorrect.
The schematic (closed loop):
Thank you in advance,
Joost