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Simulators >> Circuit Simulators >> Local loop stability analysis issue (schematic attached)
https://designers-guide.org/forum/YaBB.pl?num=1452911993

Message started by flyingRabbit on Jan 15^th, 2016, 6:39pm

Title: Local loop stability analysis issue (schematic attached)
Post by flyingRabbit on Jan 15^th, 2016, 6:39pm

Hi, below schematic is a fully-differential gain-boosting opamp that I'm working on right now.

I want to check the stability of a local loop that is comprised of gain-boosting amp and a source follower. So, I inserted 'diffstbprobe (red color)' as below, set it as a probe instance, and ran stb simulation (for now, I'm using ideal CMFB, so didn't use pstb).

However, the dc gain of this loop turned out to be 2.8, which is far different from my expectation. I've thought that this dc gain should be close to the gain of boosting amp, which is 114.

Please let me know if you find any mistake or wrong simulation setup.
Thank you in advance.