Instrumentation amplifier

Nodal analysis

Vz = R3/(R2 + R3)*Vy;

(Vz - Vx)/R2 = (Vout - Vz)/R3;

Vout = (R3/R2)*(Vz - Vx) + Vz = (R3 + R2)/R2*Vz - R3/R2*Vx = R3/R2*(Vy - Vx);

Vy - Vx = -(V1 - V2)*(Rgain + 2*R1)/Rgain;

Vout = -(V1 - V2)*[(Rgain + 2*R1)/Rgain]*(R3/R2);