10µH RF Choke Inductor
A small-value inductor whose high reactance at radio frequencies makes it useful for blocking RF signals from a DC supply line while passing DC freely — a role defined by frequency, not just inductance value.
How this component works
An inductor is a passive component that stores electrical energy in a magnetic field when electric current flows through it. Because it takes time for the magnetic field to build and collapse, an inductor inherently opposes any rapid changes in current.
In DC circuits, an inductor initially acts as an open circuit when power is applied, but eventually becomes a near-perfect short circuit once the magnetic field stabilizes. In AC circuits, its resistance to alternating current (called reactance) increases as the frequency of the AC signal increases.
Deep Dive: 10µH RF Choke
The entire reason a 10µH value gets specified is a targeted reactance calculation, not an arbitrary round number. Using XL = 2πfL, at 100MHz this inductor presents roughly 2π × 100,000,000 × 0.00001 ≈ 6,283Ω — a high enough impedance to meaningfully block RF energy from passing through, while at DC it looks like a near-short (just its wire resistance, typically under 1Ω). That combination — pass DC, block RF — is precisely the job description of an RF choke, most often placed in series with a power-supply line feeding an RF amplifier or oscillator stage so that RF energy generated by the circuit doesn't leak back down the supply rail and couple into other parts of the system.
The value also has to respect a practical ceiling: real inductors have parasitic winding capacitance that, combined with their inductance, creates a self-resonant frequency (SRF) above which the component stops behaving inductively at all. Small-value chokes like this 10µH part are wound specifically to push that SRF safely above the intended RF operating band; a much larger inductor (like the 100mH part in this category, intended for audio frequencies) would self-resonate at a far lower frequency, making it useless — and unpredictable — as an RF choke.
Common Use Cases
- RF choke in a power-supply feed line to an RF amplifier stage, blocking RF from leaking back into the DC rail
- Front-end filtering in a radio receiver, isolating the antenna/tuning stage from the supply
- High-frequency switching noise suppression in series with a DC line near a fast-switching IC
Frequently Asked Questions
Why does a small 10µH inductor block radio-frequency signals so effectively?
Inductive reactance rises with frequency (XL = 2πfL). At 100MHz, a 10µH inductor presents roughly 6,283Ω of impedance — high enough to sharply attenuate an RF signal trying to pass through it — while at DC (0Hz) that same inductor presents essentially zero resistance, letting DC current flow unimpeded.
Could a 100mH inductor do this same RF-blocking job even better, since it has more inductance?
No — at RF frequencies a 100mH inductor's parasitic winding capacitance causes it to self-resonate and start behaving like a capacitor well before reaching 100MHz, making its impedance behavior unpredictable. Small-value RF chokes like this 10µH part are specifically wound to keep their self-resonant frequency well above their intended operating range.
Does the specific value need to be exactly 10µH?
No — RF choke values are typically chosen to be "high enough impedance at the frequency of interest, well below self-resonance," so nearby values (1µH-100µH depending on the target frequency band) are often interchangeable within a design's margin.
Comparison Notes
This entry and the 100mH audio inductor share the same physics (XL = 2πfL) but are chosen for opposite ends of the frequency spectrum — this part is picked for negligible impedance at low frequency and high impedance in the RF band, while the 100mH part is picked for meaningful impedance already at audio frequencies, where a 10µH inductor would do essentially nothing useful.