An operational amplifier, or op amp, is a dc-coupled high-gain electronic voltage amplifier with differential inputs and a single-ended output. In essence, it boosts weak dc signals with an output potential that can be 100,000X larger than the potential difference between input terminals.
Op amps have been around since the early 1940s, existing alongside vacuum-tube circuitry, and became commercially available in the 1950s, with their solid-state cousins entering the market a decade later. They’re an essential part of any analog signal chain, often working as a crucial part of the interface between sensors and devices such as analog-to-digital converters (ADCs).