The manufacturer of the diode provides the detail information about the
diode, in the form of datasheet. The selection of diode or replacement
of diode in an application circuit becomes easy by referring the diode
datasheet specifications.
The following are the most important specifications related to a diode which are available in all the datasheets.
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| Table 1 Diode datasheet specifications |
The specifications Vf and If are maximum limits which diode can handle safely, at a specific temperature. The IR is generally specified at two temperatures to indicate the effect pf temperature on it.
To understand PIV specification, consider reverse biased diode as shown
in the Fig. 1. It is replaced by its model i.e. open circuit in the
Fig. 1(b).
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| Fig. 1 PIV rating of diode |
It
can be seen that the voltage between the two points P and Q is the
voltage across the diode in the reverse direction. This is the voltage
that diode must withstand without breakdown. The maximum value of such a
reverse voltage which diode can withstand safely is called PIV or PRV
rating of the diode.
The product of the current through diode and voltage across the diode,
at a particular point of operation is the power dissipation across the
diode.
PD = VD ID
The maximum value of PD i.e. PDmax
which diode can withstand safely, without increasing the temperature
of the junction above its limiting value is called power dissipation
rating of the diode.
The values of CD and CT indicate capacitance levels of the diode.
If the diode is going to be switched from ON to OFF and OFF-ON in the
circuit frequently then the reverse recovery time is important
consideration. This specification is important for the switching diodes
and not much important for general purpose rectifier diodes.
The TJ indicates the safe range of junction temperature, which should not be exceeded while the circuit operation. The Tstg indicates the safe rang of storage temperature.
