what is zero and pole circuit?

Status
Not open for further replies.

RETGT

Banned
Joined
Nov 12, 2016
Messages
161
Helped
0
Reputation
0
Reaction score
0
Trophy points
16
Activity points
0
Hello,
What is this zero and poles circuit ....
 

Hi,

From the little I know, op amps with feedback can become unstable and oscillate due to poles and zeroes, something or other about unity gain at the crossover frequency. A zero introduces a phase shift of +90º and boosts the gain by some amount in dB, a pole introduces a phase shift of -90º and decreases gain by some amount in dB, you add poles and zeroes to make your op amp circuit stable over the frequency of operation needed.

A right-half plane zero is extremely unwelcome in your circuit, it gives gain boost but phase lag, if I remember well. Voltage feedback amplifiers and current feedback amplifiers have different behaviours r.e. poles and zeroes, and both have their pros and cons (often used and detailed in SMPS circuits).

I think the idea is to set the dominant pole about (depending on who you read) one tenth to one fifth the operating frequency.

Feedback networks, control theory, pi control, pid control, error amplifier feedback/stability are some terms you can read about to understand it better.

I don't know much about it, to be honest, just that it's hard to implement.
 
Hi,

I forgot to say in previous post, the theory is to aim for 45º to 70º phase margin, one reduces ringing and the other overshoot, so a happy medium would be approx. 60º.
 
Status
Not open for further replies.

Similar threads

Cookies are required to use this site. You must accept them to continue using the site. Learn more…