Operational Amplifier (1)

Electricity and Magnetism Level 2

Consider the operational amplifier circuit above. If the voltage at the non-inverting input of the OpAmp is a b \dfrac{a}{b} volts, where a a and b b are positive coprime integers, enter a + b a+b .


The answer is 7.

Charley Shi by Charley Shi , 19, New Zealand

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

Steven Chase
Nov 10, 2020

For an ideal op-amp circuit with negative feedback, there are two "golden rules":

1) The voltages at the two inputs (inverting and non-inverting) are equal
2) The currents into the two inputs are zero

We know that the current into the non-inverting input is zero.

2 − V + 100 + − 1.2 − V + 100 + 3.2 − V + 100 = 0 \frac{2 - V_+}{100} + \frac{-1.2 - V_+}{100} + \frac{3.2 - V_+}{100} = 0

Solving results in V + = 4 3 V_+ = \frac{4}{3}

2 Helpful 1 Interesting 1 Brilliant 0 Confused

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...