This document provides an introduction to operational amplifiers (op amps) in basic electric circuits. It discusses why op amps are included early in circuits coursework given their low cost and wide applicability. The ideal op amp model is presented, where input resistance is infinite and output resistance is zero. Using this model, examples show how op amps can be used for voltage gain, signal summing, isolation, and non-inverting applications. Key equations are derived relating the output voltage to input voltages and resistor values in different op amp configurations.