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Stability of the BGR?

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sudheer_vlsi

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Hello all,

I want to simulate the stability of the BGR.what i do is checking only the stability of the Error amp used in BGR.if i want to check the stability of the whole BGR,how to simulate that.
please answer me.
 

paulux

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Break the loop by opening the -ve input of error amp and then inject a small signal.
 

bsrivastava

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Only checking the stability of op-amp wouldn't help you. You have to check the stability of the loop and which will be different.
One way is to break the loop at the inputs of op-amp and apply AC source there. This is the check for stability in frequency domain. If you can see the amount of negative feedback is more than positive feedback you are pretty much safe.
Another way of checking the stability analysis in time-domain is give the Vpwl (piece wise linear) and see the transient response. if the output settles down within you specifications, I think you are done.

thanks
-Bharat
 

sudheer_vlsi

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Thanks,Paulux and srivastava.ur replies will help me.
 

liuyonggen_1

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bsrivastava said:
Only checking the stability of op-amp wouldn't help you. You have to check the stability of the loop and which will be different.
One way is to break the loop at the inputs of op-amp and apply AC source there. This is the check for stability in frequency domain. If you can see the amount of negative feedback is more than positive feedback you are pretty much safe.
Another way of checking the stability analysis in time-domain is give the Vpwl (piece wise linear) and see the transient response. if the output settles down within you specifications, I think you are done.

thanks
-Bharat
if the pathes for positive feedback and negative feedback are the same ,can the system be stable?
 

paulux

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Hi liuyonggen_1
What do you mean by "the pathes for positive feedback and negative feedback are the same"? Please clarify
 

scottieman

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bsrivastava said:
Only checking the stability of op-amp wouldn't help you. You have to check the stability of the loop and which will be different.
One way is to break the loop at the inputs of op-amp and apply AC source there. This is the check for stability in frequency domain. If you can see the amount of negative feedback is more than positive feedback you are pretty much safe.
Another way of checking the stability analysis in time-domain is give the Vpwl (piece wise linear) and see the transient response. if the output settles down within you specifications, I think you are done.

thanks
-Bharat
Thanks Bharat first.

Personally, I suggest to use time-domain method to see whether your design is stable or not. BECAUSE, it is the most accurate method :)

However, the AC-method or frequency-domain method do give us a insight on how to design a stable system in terms of its open-loop response.

Scottie
 

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