Avalanche Transistor

avalanche transistor [′av·ə‚lanch tran′zis·tər]

(electronics)

A transistor that utilizes avalanche breakdown to produce chain generation of charge-carrying hole-electron pairs.

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Avalanche Transistor 

a transistor that operates stably at collector junction voltages approaching the breakdown voltage. Under such conditions, collision ionization occurs, leading to an increase in the number of charge carriers in the collector junction of the transistor. Stable operation of avalanche transistors in the near-breakdown region is due to the greater uniformity of electric field distribution over the area of the collector junction. Avalanche transistors are manufactured using epitaxial p⁺-p and n ⁺-n structures; the base region of the transistor is produced by diffusion methods.

Peculiarities of avalanche transistors are the possibility of obtaining a negative resistance in the emitter-collector circuit and the rapid current buildup in the circuit. Avalanche transistors are used in generators of short pulses with a steep front; they make relatively simple the shaping of powerful current pulses (up to several amperes) with a pulse rise time of less than 10^–9 sec. The possibility of generation by avalanche transistors of short pulses with a repetition frequency of up to 100 megahertz is used in coincidence circuits and sampling oscilloscopes. The existence of a region of negative resistance in the current-voltage characteristic of an avalanche transistor and the low effective value of the charge carrier transit time (from emitter to collector) make possible the use of such transistors in oscillators and amplifiers of electric oscillations in the decimeter and centimeter wavelength bands.

IU. A. KUZNETSOV