# designing opamp given Vo and Vi relation- Due in 2 days!

Discussion in 'Homework Help' started by canadaopamper, Jun 8, 2008.

Jun 8, 2008
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I have just started learning opamps in an introductory course. I am stuck at a question that asks to draw an opamp circuit such that Vo=2Vi + 3 dVi/dt

My guess would be to use differentiator circuit. But another type of opamp shud be attached to the input of the differentiator configuration to give the 2Vi.

Vo=output voltage. Vi=input voltage

Am i thinking right?
Thanks.

2. ### circuitashes Active Member

May 13, 2008
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You could use a circuit with two stages:

Stage 1: feed $V_{i}$ into the inverting inputs of a differentiator(where the product RC = 3) and an inverting amplifier (with a gain of -2).
The outputs are -RC(d$V_{i}$/dt) and -2$V_{i}$.

Stage 2: feed the two outputs of stage 1 into the inverting input of an inverting summer. This sums the inputs and inverts them to give:
$V_{o}$ = 2$V_{i}$ + RC(d$V_{i}$/dt), where RC=3

NB: The non-inverting inputs of all three differential amps in both stages must be grounded.

May 13, 2008
37
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