Matrix - Electronic Circuits and Components

<^< Worksheet: Diode Characteristics | Course Index | Examples: Zener Diodes >^>

Graph showing Zener diode characteristics

Zener diodes are heavily doped silicon diodes which, unlike normal diodes, exhibit an abrupt reverse breakdown at relatively low voltages (typically less than 6V). A similar effect occurs in less heavily doped diodes. These avalanche diodes also exhibit a rapid breakdown with negligible current flowing below the avalanche voltage and a relatively large current flowing once the avalanche voltage has been reached. For avalanche diodes, this breakdown voltage usually occurs at voltages above 6V. In practice, however, both types of diode are referred to as zener diodes. A typical characteristic for a 5.1V zener diode is shown.

Whereas reverse breakdown is a highly undesirable effect in circuits that use conventional diodes, it can be extremely useful in the case of zener diodes where the breakdown voltage is precisely known. When a diode is undergoing reverse breakdown, and provided its maximum ratings are not exceeded, the voltage appearing across it will remain substantially constant (equal to the nominal breakdown voltage or zener voltage) regardless of the current flowing. This property makes the zener diode ideal for use as a voltage reference or voltage regulator.

<^< Worksheet: Diode Characteristics | Course index | Examples: Zener Diodes >^>