Roy Choudhary Edition: Fourth Edition
Operational amplifiers (op-amps) are the building blocks of linear ICs. They are high-gain amplifiers that can amplify weak signals to a level that can be used for further processing. Op-amps have two inputs, an inverting input (-) and a non-inverting input (+), and a single output. They are used in a wide range of applications, including amplifiers, filters, and voltage regulators.
Here is the full piece on Linear Integrated Circuits by Roy Choudhary, Fourth Edition: