Avalanche Transistor


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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.

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

References in periodicals archive ?
In this paper, we describe an avalanche transistor circuit operating in a random pulse mode, which is observed at supply voltages very close to the threshold, [V.
n] and ENR) for the avalanche transistor circuit is compared with some other noise sources in Table I.
To demonstrate the mechanism behind the observed random pulses in the avalanche transistor circuit, we propose a phenomenological analog model, which is presented in Fig.
The subcircuit C2-R4-L-C3-R5 is inserted in the model circuit to imitate the inertial properties of the avalanche transistor.
Since an avalanche transistor consumes a high DC power and has a low pulse repetition rate, it is not a good choice for low power and high data rate UWB systems.
TABLE I TYPE OF PULSE SOURCES AND THEIR CHARACTERISTICS (5) Best Available Risetime at Type Step/Pulse Amplitude Notes Mercury switch step 70 ps 300 V max PRF = 200 Hz Avalanche transistor pulse 150 ps 12 V device selection necessary Tunnel diode step 25 ps 0.
With the evolution of technology, the variety of devices used for generating ultra-short steps or pulses has expanded to include gallium arsenide (GaAs) photoconductive switches, (3-4) mercury switches, avalanche transistors, step recovery diodes (SRD), tunnel diodes and avalanche diodes, etc.
Based on the best available rise time at amplitude in Table 1, it is clear that avalanche transistors, tunnel diodes and step recovery diodes are the best choices for low power ultra-short pulse generation.
Moreover, particular instances of the subcomponents and methodologies were also known -- avalanche transistor switches, light responsive switches, use of subcarriers in coding pulse trains, leading edge detectors, ring demodulators, monostable multi-vibrator detectors, integration and averaging matched filters, template signal match detectors, correlation d etectors, signal integrators, synchronous detectors and antennas driven by a stepped amplitude input.
Table 1 from Ross (1986) lists the avalanche transistor as one method (among others) for achieving pulse sources.
TYPICAL CHARACTERISTICS OF PULSE SOURCES Type Step-Pulse Best Available Risetime at Amplitude Mercury switch step 70 ps 300 V Avalanche transistor pulse 150 ps 12 V Tunnel diode step 25 ps 0.
Tenders are invited for supply of avalanche transistors