Limiter Diode

a semiconductor diode in which the impedance is strongly dependent on the applied voltage (or power) of superhigh-frequency (SHF) oscillations.

Limiter diodes are used mainly in devices for stabilizing the power level of SHF oscillations and for the protection of receivers in radar stations from the transmitter signals and irregular external radio interference. When the power level is low, the electrical impedance of a limiter diode is determined by the capacity of the diode structure, the electrical resistance between the leads, and the capacity and inductance of the envelope of the device. When the power level is high, the impedance is determined by the sum of the electrical resistances in the highly doped regions of the diode structure and in the contacts. A p⁺-n-n⁺ structure is usually used in a limiter diode, and the thickness of the n region and the impurity concentration in the region are such that the space-charge region of the p⁺-n junction adjoins the n-n⁺ boundary. Limiter diodes have a maximum power dissipation of 0.2–1.0 watt and a capacitance of 0.2–2.0 picofarads.