A standard diode can fail and cause damage when a signal’s voltage becomes too high, but an avalanche diode intentionally initiates the avalanche effect to conduct excessive power away from the circuit to ground. Avalanche diodes are used to protect circuits from unwanted or unexpected voltages.
Diodes are devices that block the passage of an electrical signal in one direction, but allow the passage of a signal in the other. When a standard semiconductor diode blocks a signal, it is possible for that signal’s voltage to become too high for the diode to control. At that point, the diode will fail and allow the signal through and will likely be destroyed as the voltage drives it through. Nicknamed the diode snowball point, once this effect begins, it usually doesn’t stop until it’s run its course, wreaking havoc on many, if not all, circuit components in its path. An avalanche diode is a special type of diode that is able to resist the avalanche event and utilize the avalanche effect in its normal function.
All semiconductor diodes consist of two pieces of semiconductor material, usually silicon, fused together. One piece of the material, the cathode, will have a positive charge. The second piece, the anode, will have a negative charge.
These diodes control the direction of circuit flow in circuits. When an electric current is applied to the anode of the diode, it flows through the positively charged material to the negative cathode and then travels from the cathode to the rest of the circuit. A diode operating in this state is forward biased.
If the same current is connected to the cathode, it will simply stop with the identical charge of the cathode and be blocked by the diode. A diode in this state is reverse biased. If that voltage is high enough, however, it can have enough power to jump across the cathode and reach the positive anode. If this occurs, current will be conducted out of the anode of the diode and the diode will be in an avalanche condition. This condition generally destroys a standard diode, as well as any other circuit component that is between the diode and a ground point.
An avalanche diode is very specifically designed so that the avalanche effect can be used. Instead of waiting for the voltage to get too large for the diode to handle and avalanche out of control, an avalanche diode intentionally initiates the avalanche effect at a predetermined voltage. This predetermined voltage is not strong enough to damage the diode, which allows the avalanche diode to conduct excessive power away from the circuit to ground. In this way, an avalanche diode works in much the same way that a spillway allows a dam to redirect excessive floodwater.
The avalanche diode sees frequent use in circuits to provide protection against unwanted or unexpected voltages that could otherwise damage circuits. Such diodes usually have their cathodes connected to the main electric current path of the circuit and the anodes to an electrical ground. This configuration allows them to redirect threatening voltages directly to ground, rather than allowing them to travel through the circuit and destroy it. Avalanche diodes in this configuration act as clamping diodes as they clamp, or clamp, the maximum voltage a circuit will experience at a pre-set level.
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