nanohenries

Nanohenry (symbol nH) is the SI unit of inductance equal to one billionth of a henry. It is used to describe very small inductances, common in high-frequency electronics. The henry is the inductance of a circuit in which a current change of one ampere per second induces an electromotive force of one volt, so 1 nH = 1 × 10^-9 H.

Applications and context: Nanohenries are typical for RF inductors, on-chip inductors in integrated circuits, and high-frequency filters. Inductors at this scale are sensitive to parasitic elements and physical layout; tolerances and temperature coefficients can significantly affect performance. In practice, designers use nanohenries for impedance matching, frequency-selective networks, and as part of tuners and extenders in GHz-range circuits.

Relation to impedance: The inductive reactance is X_L = 2π f L; at f = 1 GHz, a value of 1 nH yields about 6.3 ohms, and at 100 MHz about 0.63 ohms. These numbers illustrate why nanohenries are relevant primarily at high frequencies where even small inductances produce measurable impedance.

Measurement and standards: Nanohenries are measured with LCR meters or impedance analyzers. Common tolerances range from a few percent to tens of percent, depending on construction (air-core, ferrite, or on-chip inductors) and manufacturing process. Temperature coefficients can be significant, affecting inductance with operating temperature.

See also: Inductance, Henry, Microhenry, Picohenry.