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Integrator

Op-amps and analog ICs · Advanced · about 20 minutes · part of Zen’s Electronics Design Mastery

Put a capacitor in the feedback path. The input current V_in/R charges it at a steady rate, so the output ramps: V_out = −(1/RC)∫V_in dt. A square wave in gives a triangle out. The 1 MΩ across C stops slow drift.

Integrator: the circuit on the simulator's bench

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How it works

Slope while the input is +1 V: dV/dt = −V/(RC) = −1 kV/s

Each half-period lasts 5 ms, so the triangle spans V/(RC) × T/2 = 5 V peak to peak

It settles around 0 V with time constant R_leak·C = 100 ms.

Try it on the bench

  1. Halve the frequency to 50 Hz: the ramps run twice as long, so the triangle doubles.
  2. Switch the source to a sine: the integral of a sine is a cosine, shifted 90°.

Parts on the bench

In the course

Zen’s Electronics Design Mastery, module “Op-Amps & Analog ICs”.

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