# Circuit design problem

Discussion in 'Homework Help' started by boks, Oct 26, 2008.

1. ### boks Thread Starter Active Member

Oct 10, 2008
218
0
A circuit has input voltages V1 and V2. Design the circuit so that Vo becomes

Vo = 10 INT(V1 dt) - 5V2. The input resistance of both voltage sources should be at least 100k(ohms). Assume ideal op-amp.

I have no idea where to start in this problem. Any hints?

2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
Well, the first part of the equation is an integration function, thus you have to build an integrator circuit. The second part is a non-inverting amplifier with a gain of 5. Then you have to connect these two circuits to the inputs of a differential amplifier, with the integrator output connected on the non-inverting input and the non-inverting amplifier on the inverting input of the differential amplifier, to take the final expression on the output of the differential amplifier.

3. ### boks Thread Starter Active Member

Oct 10, 2008
218
0
Isn't the second part an inverting amplifier, since there's a minus?

4. ### mik3 Senior Member

Feb 4, 2008
4,846
63
No, the minus will come later from the differential amplifier.

5. ### boks Thread Starter Active Member

Oct 10, 2008
218
0
Can I also design an adder?

Last edited: Oct 26, 2008
6. ### mik3 Senior Member

Feb 4, 2008
4,846
63
Yes, that's a better solution because you wont need an inverting amplifier on the output of the integrator with a gain of 1 to make the inverting output of the integrator non-inverting and obtain the positive sine on the equation.

Oct 10, 2008
218
0

Feb 4, 2008
4,846
63

Oct 10, 2008
218
0
10. ### mik3 Senior Member

Feb 4, 2008
4,846
63
That looks fine.

11. ### boks Thread Starter Active Member

Oct 10, 2008
218
0
According to the solutions manual, what I should do is to couple an integrator and an inverting summing amplifier (adder).