What Is an Avalanche Transistor?

Jean Marie Asta
Jean Marie Asta
Scientist with beakers
Scientist with beakers

The bipolar junction avalanche transistor, or simply the avalanche transistor, is designed to operate in the region of a radio transmission system known as the avalanche breakdown region. This particular region has the characteristics of avalanche breakdown, which means impact ionization occurs at pairs of electron holes and some electric flow occurs in the system. Its electric field that is in a diode’s depletion zone may be high and the electrons that enter this zone accelerate at tremendous speeds. The accelerated electrons can collide into other atoms, knocking electrons from bonds with other atoms to create more pairs of electron holes and, consequentially, more current. This effect is similar to the natural phenomenon of an avalanche and is the reason behind the name "avalanche transistor."

This type of transistor can be triggered and operate under different modes, including avalanche breakdown as well as current mode breakdowns. It may use different modes of generation such as fast pulsed, optical and electrical, amongst others. An avalanche transistor can also operate at varying radio frequencies, ranging between 0.5 and 3.0 gigahertz (GHz) with a three terminal power amplifier that is linear. The power amplifier gains power via avalanche multiplication, with the amplifier’s collector using transit time. Though the range is much smaller, the amplifier is capable of transmitting frequencies up to 10 GHz.

The avalanche transistor model is often seen in a type of radio transmission system that is spread spectrum. Discrete components of frequency signals fall under noise levels and cannot be discerned by standard radio reception equipment. The signals used for communications are often narrow and do not cover a very wide spectrum. An avalanche transistor expands this spectrum, opening up the availability of communication signals between 10 and 100 times the standard availability. The energy, however, of these signals is significantly lower than noise levels, especially those of available standard communication signals.

This low energy that avalanche transistor signals emit is beneficial because it does not interfere with other signals or operations of electronic components. In addition to this kind of approach, modulations of coded sequence are employed to make links of communication signals non-interfering to other signals. The modulations may also be adjusted, manipulated and turned on or off. Turning avalanche mode of this transistor on allows it to operate a switch made of semiconductor material, which is powered by delay lines or other power sources with short duration.

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    • Scientist with beakers
      Scientist with beakers