#### electronicsLearner77

- Jul 2, 2015

- 306

- Joined
- Jul 2, 2015

- Messages
- 306

It is part of the actual and bigger schematic. I tried to simplify the circuit as below, i am not sure of the effect of capacitor C1 hence as first step i removed it and analyzed

Assuming ideal op amp configuration V+=V-, I+ = I-=0; And let V0 be the voltage at the output

V1 - I1*R2 - I1R1+ V0 = 0 --> eq1

V2 - I2*R3 - I2R7 - Vref = 0 --> eq2

V1 - I1*R2 = V2 - I2*R3 --> eq3

Simplifying eq3

V1 -V2 -I2 * R3 = I1*R2 => I1 = (V1 - V2 - I2*R3)/R2 --> eq4

Substitute eq4 in eq1

I1(R1+R2) = V1+V0

(V1-V2-I2*R3)(R1+R2)= R2*(V0+V1)

V1 - V2 - I2R3 = R2(V0+V1)/(R1+R2)

{V1-V2 - R2(V0+V1)/(R1+R2)}/R3 = I2 -->eq5

substitute eq5 in eq2

I2(R3+R7) = V2-Vref

{V1-V2-R2(V0+V1)/(R1+R2)}(R3+R7)/R3 = V2 - Vref

The final output comes as

V0 = V1(R1/R2) - {V2(R1+R2)/R2(2R3+R7)}/(R3+R7) + {Vref*R3*(R1+R2)}/{(R3+R7)R2} -->eq6

I am not sure it is a very big equation, i cannot directly understand the dependence of V0 on the input signals? And what is the effect of capacitance?