How To calculate the feedback resistors in an OpAmp Amplifier?

[Shahriar]

Hi

Imagine that you want to build an Inverting OpAmp Amplifier with the Gain of 30. What is the difference if I choose two resistor as

(Rf=100K, R1=3.3K) or  (Rf=10K, R1=330R). In both cases the Gain is 30, but In what conditions, does it make difference? and what about a Non-Inverting One?

ThanX
Shahriar

 

[MP1]

You are changing the input resistance and thus changing the input impedance. The input resistor could also be used as part of the input filtering such as a resistor/capacitor filter. The value would need to be correct for the cut point. In all cases, the input resistor is determining the current (V/R=I). All of the above are the reason that it makes a difference. You should design with all of these items in mind.

MP

 

[Shahriar]

Yeah, That's Right  ;D