Why the output may appear overshoot and ringing?

[xiexi]

About the overshoot

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.

 

[rongli]

About the overshoot

someone say that is the reflection of the high frequency wave.

 

[bastos4321]

Re: About the overshoot

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.


Bastos

 

[muldersun]

About the overshoot

I think the phase margin is not enough,you can debug the r2 and c1 to solve the problem

 

[defe_song]

Re: About the overshoot

You can increase C1.

 

[eda4you]

Re: About the overshoot

Measure your phase margin using a bode plot!

I alos think that C1 is much to small --> C1 ~ 10-50 pF


Alos decreasing C2 will help you.

 

[xiexi]

About the overshoot

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.