4 Effects of feedback from a amplifier

[Englewood]

I need to EXPLAIN 4 different effects of feedback on the function amplifier,

I know distortion and noise are improved by feedback.

I know it can increase the input impedance to the point where it is infinite.

 

[treez]

FEEDBACK...
helps you get an exact lower gain than the open loop gain
helps you have stability as long as you do it right...it must be negative feedback.
the input of an opamp without feedback is infinite...with feedback, I thought it was less.

 

[LvW]

1.) Closed-loop gain < open-loop gain
2.) Increase/decreaase of input resistance for non-invertingIinverting operation
3.) Lowering of output impedance
4.) Improvement in distortion and linearity
5.) Reduction of input offeset errors (referred to the output)
5.) Negative feedback causes dynamic stability degradation (without feedback no stability problems).

 

[Englewood]

How about comparing the practical performance of two different classes of amplifiers

 

[LvW]

How about comparing the practical performance of two different classes of amplifiers

Which classes?

 

[Englewood]

Which classes?

Class A + B

 

[Audioguru]

the input of an opamp without feedback is infinite.

Absolutely NOT for ordinary opamps that use bipolar transistors on their input.
The input resistance of an old 741 opamp is a minimum of 300k ohms but is typically 2M ohms.

Opamps with Jfet or Mosfet input transistors have extremely high input resistance.