RL low-pass filter calculator

Calculate RL low-pass cutoff, voltage gain and phase across the resistor.

Schematic

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Results

Cutoff frequency1.59 kHz

Frequency response

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Voltage gain	0.85 V/V
Phase shift	-32.14°
Output amplitude	846.73 mV

Advanced results

Time constant	100 µs
Gain	-1.45 dB
Input current amplitude	846.73 µA

How rl low-pass filter works

A series inductor and shunt resistor pass low frequencies. As frequency rises, the inductor’s reactance rises and less of the input voltage appears across the resistor.

f_c=\frac{R}{2\pi L}

Ideal inductor and resistor, ideal source and unloaded output across R1. Winding resistance is excluded.

Change the form inputs or click a component value on the schematic. Choose Try in CircuitSim to simulate the configured circuit.

Do the math

Selected input values
L1	100 mH
R1	1 kΩ
V1	1 V
Frequency	1 kHz

Time constant: $\tau=L/R$
$\frac{100\,\mathrm{mH}}{1\,\mathrm{k\Omega}}$
≈ 100 µs
Cutoff frequency: $f_c=\frac{1}{2\pi\tau}$
$\frac{1}{2\pi\times 100\,\mathrm{\mu s}}$
≈ 1.59 kHz
Output amplitude: $V_{out}=|H(f)|V_{in}$
$0.85 \times 1\,\mathrm{V}$
≈ 846.73 mV

RL low-pass filter calculator

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Schematic

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How rl low-pass filter works

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