Here is another tip of the hat tip of the soldering iron to one of the Planet Analog archived posts. This post gives an explanation of how op-amps work in general and how an integrator works in ...

Op amps are very-high-gain amplifiers with differential inputs and single-ended outputs. They are often used in high precision analog circuits, so it is important to measure their performance ...

Bob Pease got an e-mail in 2006 from an engineer who was having trouble with an integrator circuit. Amplifiers are often called op amps because they were originally used as operational amplifiers.