# Ideal Op Amp

For the circuit shown, assume an ideal op-amp. Find vo(t). Also, find the maximum value of vo(t). See attached diagram. Show how you arrived at your answer.

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## SOLUTION This solution is **FREE** courtesy of BrainMass!

The Op- amp is configured in Inverting and Non inverting mode. We need to apply the gain formulae for the two configurations. To find the total output, by superposition law, add the two outputs and that should be it.

Vo (inv) = ( -Rf/R1 )V1

Vo (Non-inv) = (1 + (R2/R1) )V2

Given:

Rf = feedback resistor = 20k

R2 = 20K resistor at the +Ve terminal

R1 = 1K (Resistance at both the input terminals)

We know V1 and V2

So,

Vtotal = 0.05 * (21/1) Sine (2pi*1200t) - 0.1 * (20/1) sin (2pi*60t)

take 0.05* 21 approx = 1,

Just by solving and observation,

c) is your answer.

To find Vo max,

We know

Vo total = 0.05 * (21/1) Sine (2pi*1200t) - 0.1 * (20/1) sin (2pi*60t)

max of this term occurs when

a) The Sine (2pi*1200t) term = 1 ; which means (2pi*1200t) = 90 degree

and

b)the sin (2pi*60t)= 0; which means (2pi*60t)= = 0 degree

If the above conditions are met,

Vo max = 1 - 0 = 1V

answer is C

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Hope this helped.

Regards

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