**Subtractor using Op Amp or Difference Amplifier Circuit:**

Similar to the summer circuit, the subtraction of 2 input voltages is possible with the help of op-amp circuit called subtractor or difference amplifier circuit. The Subtractor using Op Amp circuit diagram is shown in the Fig. 2.31.

To find the relation between the inputs and output let us use Superposition principle.

Let V_{o1} be the output, with input V_{1} acting, assuming V_{2} to be zero. And V_{o2} be the output, with input V_{2 }acting, assuming V_{1} to be zero.

With V_{2} zero, the circuit acts as an inverting amplifier. Hence we can write

While with V_{1} as zero, the circuit reduces to as shown in the Fig. 2.32.

Let potential of node B be V_{B}. The potential of node A is same as B i.e. V_{A} = V_{B}. Applying voltage divider rule to the input V_{2} loop,

Equating the equations (3) and (4),

Substituting V_{B} from (2) in (5) we get,

Hence using Superposition principle,

Now if the resistances are selected as R_{1} = R_{2},

Thus the output voltage is proportional to the difference between the two input voltages. Thus it acts as a Subtractor using Op Amp circuit or difference amplifier.

If R_{1} = R_{2} = R_{f} is selected,

But by selecting proper values of R_{1}, R_{2} and R_{f}, we can have the subtraction of two inputs with appropriate strengths like