When the amp's some transistors work in the non-saturation region, and the amp is connected as unity gain buffer, when input small pulse, the output will appears overshoot and ringing, why it is so? Does the phase margin reduce? If it is so, how can the low gain influence the poles and zeros?
Hopefully you can give me intruction more detail, perhaps using the 7 transistor to demonstrate will be clearer. Thank you ahead.
The overshoot is related to the PM you have in unity configuration. For a PM higher than 63º you should not have any overshoot in a well designed amplifier.
Maybe you don't know my meaning, when the transistors are all in saturation, the phase margin is above the 60 well, but if the common input voltage is too low, the M2&M3 is in non-saturation, the output will overshoot, my boss only give me the hint that the amp with feedback can't reponse quickly, but I can't catch the detail.