2.1 What is an Op-Amp?

An Operational Amplifier, or Op-Amp, is a direct-coupled, high-gain amplifier packaged as an integrated circuit. It is designed to perform a wide variety of linear, non-linear, and mathematical operations and can be used with both AC and DC signals.

2.2 The Basic Structure

An op-amp has two input terminals and one output terminal. The input terminals are the key to its operation:

• Inverting terminal: An input signal applied here will produce an output signal that is 180 degrees out of phase with the input.
• Non-inverting terminal: An input signal applied here will produce an output signal that is in phase with the input.

While all op-amps share this basic structure, the best way to understand them is to compare a perfect, theoretical model with a real-world, practical one.