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feedback factor beta

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nodame123

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Why can't beta(feedback factor) be greater than 1 (in negative feedback)? I have read it somewhere and understood long back.Something like what's the use of amplifying or feeding more than the output,and the input to the integrator can't be -ve or something. I have forgotten why exactly,can someone help fill the gap?
 

The feedback factor is larger than unity if it is not a PASSIVE but an ACTIVE feedback path (with another amplifying unit).
Example: Phase-lead integrator. In this circuit the feedback path consists of an inverting opamp amplifier in series with the integrating capacitor - fed back to the non-inv. opamp termnal.
Advantages: The parasitic phase shift of the feedback opamp can - partly - compensate/neutralize the parasitic phase shift of the main opamp.

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I forgot to mention: Of course, this is a non-inverting integrator. (Using the same principle we can create a phase-compensated non-inverting gain stage).
 

okay. My question was about why do we mostly see passive feedback? Why can't we replace the passive fb with active,for example? Instead of feeding 20% of output why not 200% ? Is there any technical difficulty if there is an integrator in the forward path,as in the simple case.Can you answer it in that perspective?
 

okay. My question was about why do we mostly see passive feedback? Why can't we replace the passive fb with active,for example? Instead of feeding 20% of output why not 200% ?

Of course, we can. But why should we? Do YOU see any advantage for feeding back 200% ?
 

No,I don't.The proper explanation for that is what I am looking for.
Different perceptions is what I need.
 

No,I don't.The proper explanation for that is what I am looking for.
Different perceptions is what I need.

Do you know the closed-loop gain value of an amplifier with a feedback factor larger than unity?
 

No,I haven't studied such a circuit yet.
 

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