michaelFCT
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Posts: 9
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Hi,
I designed a 2 stage amplifier (with compensation) and when simulated (setup in attachment) using tran, it shows that the output common-mode of the amplifier is unstable. I then used STB (substituting the SC-CMFB for an equivalent RC circuit) and PSTB, using the actual SC-CMFB, and placed the cmdmprobe (cmdm=1) at the output of the amplifier, thus breaking all loops in the circuit. STB and PSTB analyses always return a PM > 65º. The DC OP point has been preserved, and the circuit is also unstable for Vin=vss (without stimulation).
Why can't I detect this instability? Is there something wrong with the setup?
Thanks in advance.
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