Dynamic RC Low-Pass Filter

Analog

A first-order shunt-capacitor filter. The cutoff and the $|H(j\omega)|$ magnitude are derived live; the output wire fades its opacity and stretches its dash pattern to visualise physical damping, and both channels drive the oscilloscope.

Live circuit passband tracking

Drag a value tag to change that part. Click a wire to clip a probe on.

Causal signal trace paused

Apply $V_{\mathrm{in}}$ The source establishes the stimulus and the return reference.

t_{\mathrm{stage}}=\htmlData{math-slot=value}{\mathtt{0.00}}\,\mathrm{s}

Step 1 / 4 Apply Vᵢₙ

Notebook: 6 parts and 6 wires, modelled as frequency-domain transfer function

Recommended lab 2 of 18

Predict how component values move a first-order pole and attenuation.

Prerequisite: none — start here.

Predict, then test

Keep $R$ fixed and increase $C$ . What happens to the cutoff $f_c$ ?

Commit before the explanation appears. This is a prediction, not a quiz score.

Governing model

f_c = \dfrac{1}{2\pi RC} \;\cdot\; |H(j\omega)| = \dfrac{1}{\sqrt{1 + (f/f_c)^2}}

Parts

input source node
series resistor $R$
shunt capacitor $C$
reference ground

Limits of the model

$R: 100\ \Omega$ – $1\ \mathrm{M\Omega}$
$C: 1\ \mathrm{nF}$ – $10\ \mathrm{\mu F}$
sweep $10\ \mathrm{Hz}$ – $100\ \mathrm{kHz}$

Diagnosis challenge The fault is hidden. Work it out from the changed outputs first.

Notebook: 6 parts and 6 wires, modelled as frequency-domain transfer function

Keep RRR fixed and increase CCC. What happens to the cutoff fcf_cfc​?

Keep $R$ fixed and increase $C$ . What happens to the cutoff $f_c$ ?