Avalanche Diodes Information
Avalanche diodes are designed to break down at a specific high breakdown voltage (avalanche). These diodes are used for protection of electronic devices against high voltages. The diodes use a predetermined voltage to start the avalanche effect instead of allowing the voltage to become too large to cause damage to the diode. This allows the diode to provide the required protection for the electronic device while continuing to operate.
Avalanche diodes work on the avalanche effect which occurs when the voltage across the pn junction is greater than the design voltage. The avalanche breakdown is when the minority carriers that cross the depletion region under the influence of the electric field gain sufficient kinetic energy to be able to break covalent bonds in atoms with which they collide. The carriers liberated by this process may have sufficiently high energy to be able to cause other carriers to be liberated in another ionizing collision. This process occurs in the fashion of an avalanche, with the result that many carriers are created that are able to support in the voltage drop across the junction.
The following specifications determine the functionality of an avalanche diode.
- Forward voltage - the forward voltage at specified forward current input. It is also defined as the voltage across the diode terminals that results from the flow of current in the forward direction.
- Reverse voltage - is the maximum allowable reverse voltage that can be applied repeatedly.
- Breakdown voltage - is the reverse voltage at which a small increase in voltage results in a sharp rise of reverse current.
Microelectronic Circuits, Fifth Edition, Sendra/Smith, pg,203 - 204