Differential Amplifier (Subtractor)


Working principle

A differential op-amp amplifies the difference between two input voltages (Vin1 and Vin2).

Formula derivation

If Vin2 = 0, 

If Vin1 = 0, 

Given that:


  • Equate R1 to R3, and R2 to R4 to transform this circuit into a voltage subtractor with the output (R2/R1)*(Vin2-Vin1).
  • Equate all resistor values. What is the output in terms of the input voltages now?