Avalanche Diodes


An avalanche diode experiences and endures avalanche breakdown at a specified reverse bias voltage. The ‘avalanche point’ of any diode is the   point at which the voltage of a signal becomes too high for the diode to control. With a standard diode, this ‘overburdening’ of it leads to failure. In turn, the signal will pass through and typically will destroy the other circuit components in its path. This devastating effect is known as ‘avalanche breakdown’ – and fortunately, avalanche diodes are designed to endure this and prevent it from destroying the circuit.

A reverse-biased position is taken by an avalanche diode; a non-conducting position so it does not interfere   with the circuit in which it is being used. This means that electrical current is applied to the diode’s cathode, rather than the anode. Therefore, the current will come to rest with the cathode charge; this is the way a reverse-biased diode blocks charge. However, in the cases of very high voltage, current may be conducted out of the anode of the diode – sending it into ‘avalanche condition’.

Yet rather than ‘avalanching’ out of control and sacrificing the circuit, an avalanche diode is designed to intentionally start the process at an earlier voltage. It therefore enters breakdown at a level of voltage not strong enough to damage it and grounds any excess power. This brings the potentially harmful level of voltage to ground; essential for protecting the circuit. It is a fast process which makes avalanche diodes one of the quickest devices for surge suppression. In turn they are suited well to inductive circuits, or when diodes are being installed in series.

They are ideal for improving the reliability of electrical applications, especially where voltage transients may be a possibility. The reverse-biased position allows the diode to withstand more transients and offers protection against surges, lightning and overload.

We have large stocks of Ixys and Vishay Avalanche diodes and some bespoke Hind devices used in the London Underground. Semikron, Infineon , Eupec and other manufacturers can be sourced too. We currently have almost 2000 avalanche diodes in stock and here at High Power Semiconductors we provide a wide range of avalanche diodes, so you can choose the right response for your high voltage circuit.

These diodes also are especially durable, with a junction in the design which prevents hot spots and current concentration.   This allows the diode to remain undamaged by the process and brings voltage to a roughly similar level after breakdown, even though current may be changing.

Avalanche breakdown occurs due to high levels of ionization. Unlike regular diodes which tend to maintain a higher voltage than the breakdown, avalanche diodes experience a small but notable drop   of voltage when under breakdown conditions. This means they can keep the avalanche breakdown uniform across the whole junction and provide better surge protection than a standard diode.

When they are used industrially, typically for voltage control, they may be known as ‘transient voltage suppressors’ or ‘clamping diodes’. This is because they supress voltage from surpassing a certain level and ‘clamp’ it to a predetermined ideal. This plays a key role in keeping voltage at a suitable level so it is not too high for the circuit. Therefore, one of their major applications is as protection in large industrial systems where higher voltages are expected.

Our customers use rotating diodes for a range of reasons. Some use them as voltage reference devices, as avalanche diodes keep levels as uniform as possible; even with a changing current.

Not only are they used to give electronic circuits inbuilt protection against the damage of too-high voltages – they also capable of generating other effects. When in use, avalanche diodes can create radio frequency noise – often used within radio equipment for this reason. Other uses include smaller-scale circuits such as in random number generators, and on a larger-scale, power stations.

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