Stability of feedback systems

Status
Not open for further replies.
S

shivamgarg

Newbie level 4
Joined
Oct 29, 2014
Messages
5
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Location
College Station, TX
Visit site
Activity points
37
Folks,

Howdy !!

I have a doubt relating to stability of a system. To check stability we always assume a FEEDBACK circuit. Why is this so?
If we stabilize the circuit for open loop shouldn't it be stable for circuit with feedback as well?

Thanks.
 

Hello!

Of course it does: if there is no feedback, then you don't have much to control.
Example: input signal -> amp -> output signal. (well, there might be a closed loop in
the amp, but this is another story).
If you check for stability, it means that you have some kind of loop, the most usual
being input -> subtractor -> amp -> output and feedback to subtractor.

Dora
 

It's feedback that cause instability in a system (when the feedback becomes positive at some frequency).
How would an open loop system be unstable?
 

shivamgarg said:
Folks,

If we stabilize the circuit for open loop shouldn't it be stable for circuit with feedback as well?

Thanks.
Click to expand...
What does it mean "stabilize the circuit for open loop" ? Isn't it stable in all cases ? Maybe you mean DC stability for example in the Bandgap circuit or beta multiplier ?
 

haykding said:
What does it mean "stabilize the circuit for open loop" ? Isn't it stable in all cases ? Maybe you mean DC stability for example in the Bandgap circuit or beta multiplier ?
Click to expand...
Good point.
Shivamgarg, are you referring to AC or DC stability since they are entirely different and often unrelated(?).
 

Status
Not open for further replies.

Similar threads

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