About

In radio frequency (RF) engineering, the LC tank circuit is the fundamental building block for tuning transmitters, receivers, and filters. A specific combination of an inductor (L) and a capacitor (C) oscillates at a unique natural frequency. Precision is paramount here; a slight deviation in component values can shift a filter's cutoff point or detune an antenna system, rendering the circuit inefficient or non-functional.

This tool eliminates the common friction of manual unit conversion. Engineers typically work with Henries, milliHenries, and microHenries mixed with picoFarads or nanoFarads. The calculator automatically handles these orders of magnitude, solving the resonance formula instantly. It also supports reverse engineering: if you know the target frequency and have a fixed capacitor, it solves for the required inductance.

Formulas

The resonant frequency f₀ occurs when the inductive reactance equals capacitive reactance:

f₀ = 12π √LC

Rearranging for components:

L = 14π²f²C

Reference Data

Frequency Band	Typical L	Typical C	Application
AM Radio (530-1700 kHz)	200 µH	30-300 pF	Tuning Coil
FM Radio (88-108 MHz)	0.1 µH	20-50 pF	Local Oscillator
WiFi (2.4 GHz)	2 nH	1.5 pF	Impedance Matching
RFID (13.56 MHz)	1-2 µH	50-100 pF	NFC Antenna
Audio Crossover (1 kHz)	1 mH	20 µF	Low Pass Filter

Frequently Asked Questions

If Capacitance is extremely low, stray capacitance from the PCB traces and component leads becomes dominant, making the circuit unstable and difficult to tune unpredictably.

Generally, no. Electrolytic capacitors have high internal inductance and are polarized. For RF applications, ceramic (NP0/C0G) or mica capacitors are preferred for their stability and low loss.

The Q (Quality) factor determines the bandwidth of the resonance. A high Q results in a sharp, narrow peak (good for selectivity), while a low Q results in a broad bandwidth. This calculator assumes ideal components (infinite Q).

Yes. In a resonant tank circuit, the voltages across the inductor and capacitor can ring up to values significantly higher than the supply voltage. Ensure components are rated for these peak voltages.