The operational amplifier is one of the most useful analog ICs available, and one of the most daunting for beginners and experienced engineers.
Above is a diagram of an op-amp in a closed loop
non inverting configuration. Probably the most used configuration. Lets assume this is an ideal amplifier. R1 is the input and R2 is the feedback. When R1 = R2 the circuit is in unity(meaning input = output).
To calculate output use the following formula.
R3 can be calculated by the following.