eegchen
Member level 1
Hi,
Thank you for watching this post.
For a simple feedback, like R1=R2=R, OPAMP's gain is A.
Non-inverting feedback amplifier, the input impedance is (1+AB)*Ri, B is feedback factor.
Inverting feed amplifier , the input impedance is R+R/(1+A)
I can do some math to get the result. But how to intuitive analysis this?
The Art of electronics gave the explanation like this,
"since voltage feedback tends to subtract signal from the input,
resulting in a smaller change (by the factor AB) across the amplifier's input resistance; it's a form of bootstrapping. Current feedback reduces the input signal by bucking it with an equal current."
But i am not quite understand, anyone can give more detailed explanation?
best
Thank you for watching this post.
For a simple feedback, like R1=R2=R, OPAMP's gain is A.
Non-inverting feedback amplifier, the input impedance is (1+AB)*Ri, B is feedback factor.
Inverting feed amplifier , the input impedance is R+R/(1+A)
I can do some math to get the result. But how to intuitive analysis this?
The Art of electronics gave the explanation like this,
"since voltage feedback tends to subtract signal from the input,
resulting in a smaller change (by the factor AB) across the amplifier's input resistance; it's a form of bootstrapping. Current feedback reduces the input signal by bucking it with an equal current."
But i am not quite understand, anyone can give more detailed explanation?
best