In non-inverting amplifier configuration input voltage(VIN) is applied at the non-inverting input terminal of an op-amp. The feedback is applied at the inverting input terminal drawing current from the output through a potential divider network. This is shown in the following circuit diagram.
The gain of the non-inverting amplifier can be derived by applying the concept of virtual ground and Kirchoff Current Law at inverting and non-inverting terminals as follows.
Applying KCL at node V- and taking the fact that virtually no current flows into the op-amp,
Applying the concept of virtual ground,
But ,
Therefore,
Substituting Equation (2) in Equation (1),
Therefore voltage gain AV of the non-inverting amplifier is given by,
