Op amps were initially developed for electronic analog computers. Analog computers can be programmed to solve mathematical models of mechanical or electrical systems. These models are usually expressed in terms of differential equations.
To solve simple differential equations using the analog computer requires cascading three types of op amp circuits:
- Integrator circuits
- Summing amplifiers
- inverting/non-inverting amplifiers for negative/positive scaling.
Any differential equation can be simulated by an analog computer comprising integrators, inverters, and inverting summers. But care must be exercised in selecting the values of the resistors and capacitors, to ensure that the op amps do not saturate during the solution time interval.