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 Vin is applied directly to the non-inverting terminal while one side of resistor R1 is connected to the inverting terminal and the other side is at ground.
According to virtual short concept, V1 = V2. Since,op-amp is assumed to be ideal then no enters the input terminals. Therefore, V1 = Vin. Then V2 = Vin
The current I1 is given by
The current I2 is given by
Since currents I1 and I2 are equal, therefore
I1 = I2
The closed loop voltage gain Av is given by
From voltage gain Av, 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 Vin 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 Av of non-inverting operational amplifier also depends on the values of R2 & R1
2. The closed loop voltage gain Av 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 Av 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.