Question

If the value of resistor Rf in an averaging amplifier circuit is equal to the value of one input resistor divided by the number of inputs, the output will be equal to:

A. the average of the individual inputs
B. the inverted sum of the individual inputs
C. the sum of the individual inputs
D. the inverted average of the individual inputs

Answer 1

Answer:

D) the inverted average of the individual inputs

Explanation:

As we know input impedance is very high so input current will be zero. op amp do not sink any current

$I_{in}$ = $I_{f}$

$\frac{V_{in} }{R}$=$-\frac{V_{o} }{R_{f} }$

$V_{o}$ = - ($R_{f}$ / R) ×$V_{in}$

If R = $R_{f}$  then $V_{o}$  = -$V_{in}$, the circuit behaves like an inverter.

Output is independent of Rf