Op-amp integrators can ramp to saturation, and a capacitor-discharge switch can reset them. Alternatively, you can input-switch them to ramp up and down in triangle-waveform-generator applications.

2. The addition of an input switch allows the sample/hold (SH) to be incorporated into the integrator, and the external one can be removed. Suppose you want to integrate a 20-mV signal for 30 ms.

To implement a single-input integrator, the four resistors can have the same value. Quad equal-value resistor packs with ratio tolerances down to ±0.01% are available from Caddock Electronics.