sjamil02
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Hi all,
(1)
I have designed folded cascode Op Amp with class AB output stage based on flip voltage follower (see attachment). When I added regulated differential gain amplifiers to increase the gain, I noticed that the current in PM28 and M7 are not equal (96uA vs. 91uA). When there is no gain enhancement scheme applied, those two current branch are identical. What could be the problem? Can this affect the circuit performance? By the way, this is observed from the spectre dc operating point results.
With this gain enhancement scheme, I was able to increase the dc gain from 35dB --> 50dB with 450MHz UGF @Vdd=1.2V / 130nm CMOS. The gain and frequency responce plot seems ok.
(2) How to compensate the op amp? should I put compensation capacitor at the gate of M7 and M9 and gate of NM31?
Thanks in advanced
sj
(1)
I have designed folded cascode Op Amp with class AB output stage based on flip voltage follower (see attachment). When I added regulated differential gain amplifiers to increase the gain, I noticed that the current in PM28 and M7 are not equal (96uA vs. 91uA). When there is no gain enhancement scheme applied, those two current branch are identical. What could be the problem? Can this affect the circuit performance? By the way, this is observed from the spectre dc operating point results.
With this gain enhancement scheme, I was able to increase the dc gain from 35dB --> 50dB with 450MHz UGF @Vdd=1.2V / 130nm CMOS. The gain and frequency responce plot seems ok.
(2) How to compensate the op amp? should I put compensation capacitor at the gate of M7 and M9 and gate of NM31?
Thanks in advanced
sj