A standard specification sheet usually has a brief description of the diode. Included in this
description is the type of diode, the major area of application, and any special features. Of particular
interest is the specific application for which the diode is suited. The manufacturer also provides a drawing
of the diode which gives dimension, weight, and, if appropriate, any identification marks. In addition to
the above data, the following information is also provided: a static operating table (giving spot values of
parameters under fixed conditions), sometimes a characteristic curve similar to the one in figure 1-20
(showing how parameters vary over the full operating range), and diode ratings (which are the limiting
values of operating conditions outside which could cause diode damage).
Manufacturers specify these various diode operating parameters and characteristics with "letter
symbols" in accordance with fixed definitions. The following is a list, by letter symbol, of the major
electrical characteristics for the rectifier and signal diodes.
DC BLOCKING VOLTAGE [VR]the maximum reverse dc voltage that will not cause breakdown.
AVERAGE FORWARD VOLTAGE DROP [VF(AV)]the average forward voltage drop across the
rectifier given at a specified forward current and temperature.
AVERAGE RECTIFIER FORWARD CURRENT [IF(AV)]the average rectified forward current at a
specified temperature, usually at 60 Hz with a resistive load.
AVERAGE REVERSE CURRENT [IR(AV)]the average reverse current at a specified temperature,
usually at 60 Hz.
PEAK SURGE CURRENT [ISURGE]the peak current specified for a given number of cycles or
portion of a cycle.
PEAK REVERSE VOLTAGE [PRV]the maximum reverse voltage that can be applied before
reaching the breakdown point. (PRV also applies to the rectifier diode.)
REVERSE CURRENT [IR]the small value of direct current that flows when a semiconductor
diode has reverse bias.
MAXIMUM FORWARD VOLTAGE DROP AT INDICATED FORWARD CURRENT [V
the maximum forward voltage drop across the diode at the indicated forward current.
REVERSE RECOVERY TIME [trr]the maximum time taken for the forward-bias diode to recover
its reverse bias.
The ratings of a diode (as stated earlier) are the limiting values of operating conditions, which if
exceeded could cause damage to a diode by either voltage breakdown or overheating. The PN junction
diodes are generally rated for: MAXIMUM AVERAGE FORWARD CURRENT, PEAK RECURRENT
FORWARD CURRENT, MAXIMUM SURGE CURRENT, and PEAK REVERSE VOLTAGE.