A **non-inverting amplifier **is a operational amplifier circuit which produces amplified output signal which is in phase with the input signal.

Figure 1 shows the basic **non-inverting operational amplifier**. The input signal V_{in} is applied directly to the non-inverting terminal while one side of resistor R_{1} is connected to the inverting terminal and the other side is at ground.

According to virtual short concept, V_{1} = V_{2}. Since,op-amp is assumed to be ideal then no enters the input terminals. Therefore, V_{1} = V_{in}. Then V_{2} = V_{in}

The current I_{1} is given by

The current I_{2} is given by

Since currents I_{1} and I_{2} are equal, therefore

I_{1} = I_{2}

The closed loop voltage gain A_{v} is given by

From voltage gain A_{v}, we can see that the output is in phase with the input. Another conclusion can be drawn from above equation is that the gain is always greater than unity.

The input signal V_{in} is connected directly to the non-inverting terminal and the input current is essentially zero (ideal op-amp), the input impedance (or Resistance) seen by the source is very large (ideally infinite).

### Important points to Remember

1. The closed loop voltage gain A_{v} of non-inverting operational amplifier also depends on the values of R_{2} & R_{1}

2. The closed loop voltage gain A_{v} of a non-inverting amplifier is greater than unity.

3. The output signal is in phase with the input signal as the closed loop voltage gain A_{v} is positive.

4. Since, output and input are in same phase hence phase shift is zero.

## Non-inverting amplifier applications

1. It is used where amplified output required in phase with the input.

2. It can be used for performing mathematical stimulation such as adder.