By Kim Lewis Updated Mar 24, 2022
Inductors—metal coils embedded in electronic circuits—store energy in magnetic fields when current flows through them. When adjacent conductors carry current, these fields can induce voltages in nearby wires. A specialized type of inductor employed to suppress unwanted alternating current (AC) components in a signal is known as a choke.
Both small and large inductors can function as chokes. Their specifications include inductance value, maximum current rating, and maximum series resistance. Many chokes incorporate iron cores to enhance magnetic coupling.
Chokes act as low‑pass filters that attenuate AC ripples, allowing a downstream load—such as a resistor—to receive a clean DC voltage. They are indispensable in filtering radio‑frequency interference and smoothing power‑supply output.
The choke’s physical size determines its cutoff frequency: larger chokes exhibit lower cutoff frequencies, making them ideal for filtering mains 120 Hz hum and higher‑frequency noise, while smaller chokes target higher‑frequency rejection.
Typical choke circuits consist of a single inductor or an inductor paired with one or more capacitors. These arrangements form low‑pass filters that block high‑frequency signals while passing lower‑frequency content.
In power‑supply design, chokes eliminate AC ripple to provide a steady DC output. They also appear in oscillator topologies such as Colpitts, Hartley, and Clapp circuits, where they provide the necessary magnetic energy storage.
