| Refer to the characteristic curve of a typical
rectifier(diode) in the figure below. The forward characteristic of the curve we have
previously described above in the DIODE section. It is the
reverse characteristics we will discuss here.
Notice that as the reverse voltage is increased the
leakage current remains essentially constant until the breakdown voltage is reached where
the current increases dramatically. This breakdown voltage is the zener voltage for zener
diodes. While for the conventional rectifier or diode it is imperative to operate below
this voltage; the zener diode is intended to operate at that voltage, and so finds its
greatest application as a voltage regulator.
The basic parameters of a zener diode are:
(a) Obviously,the zener voltage must be specified. The most common
range of zener voltage is 3.3 volts to 75 volts, however voltages out of this range are
(b) A tolerance of the specified voltage must be stated. While the most
popular tolerances are 5% and 10%, more precision tolerances as low as 0.05 % are
available . A test current (Iz) must be specified with the voltage and tolerance.
(c) The power handling capability must be specified for the zener diode.
Popular power ranges are: 1/4, 1/2, 1 , 5, 10, and 50 Watts.
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