[SOLVED] op-amp oscillating with pulsed enable circuit

[zetta_byte]

For designed op-amp's enable circuit, step input results proper steady state output. But with pulse input, output is oscillating. Why so?

Thanks.

 

[KlausST]

Hi,

The enable causes the voltage to jump. And like a mechanical jump this causes some moving, sone oscillations.

It is like when you pull on a guitar string. The pulling makes no sound, and if you slowly move it back to its initial position there is no sound, too. But when you pull, and release it, the the string moves and this creates a sound with decreasing amplitude.

Klaus

 

[D.A.(Tony)Stewart]

ringing is a sign of poor gain margin at resonance or poor impedance control.

 

[zetta_byte]

Thanks for reply.

In my circuit there are two feedback and one forward path. Due to multipole compensation some poles causing that oscillations even though PM is good. I did compensation again to change the position of pole. Now there is no oscillations if i give pulse.

We always concentrate on Phase margin but I learnt how gain margin can also affect the stability.