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Op-amp differentiator

Analog Circuits Lab · free online experiment, runs in your browser with no install or sign-up.

Open this experiment in the circuit simulator

Objective

Differentiate a 1 kHz sine: the output is a cosine of amplitude Rf·C·ω·Vm.

Procedure

Run and compare the waveforms: output leads the (inverted) input by 90°.

Theory

Vout = −Rf·C·dVin/dt. With Rf = 1 kΩ, C = 100 nF and Vm = 1 V at 1 kHz: amplitude = 1 k · 100 n · 2π·1000 = 0.628 V. A 100 Ω series resistor limits the high-frequency gain.

Questions to answer

Why is a pure differentiator noisy?

Components used

2 × Battery / DC source, Ceramic Capacitor 0.1uF (104), Function generator (sine), Op-Amp LM741, Oscilloscope (2-channel), 2 × Resistor 220 ohm 1/4W

About the model

Time scale: for the browser simulator the source frequencies are divided by 100 and capacitors / inductors multiplied by 100; the waveforms keep their shape but run 100 times slower. Ideal wires; component models as listed in the catalogue (no parasitics, no temperature drift). Built without a breadboard so the schematic stays readable.