SOLUTION

There are four diode ratings that apply in one way or another to all types of diodes and applications.

1. Forward voltage drop, V_F :–The forward voltage drop (or barrier potential) is the forward-conducting junction voltage level: about 0.3 V for germanium diodes and 0.7 V for silicon. Since germanium diodes start conducting at a voltage less than 0.3 V and silicon diodes start conducting at a voltage less than 0.7 V, it should be noted that engineers might use 0.2 V for germanium diodes and 0.6 for silicon diodes. Experimental results most commonly show a 0.68 V drop for silicon. The actual voltage drop depends on the diode type and the current flowing through the diode.
2. Average forward current I_o:-This is the maximum amount of forward conduction that the diode can carry for an indefinite period of time. If the average current exceeds this value, the diode will overheat and eventually destroy itself (thermal breakdown).
3. Peak reverse voltage,V_R:– The peak reverse voltage (PRV) is sometimes called the reverse breakdown voltage or peak inverse voltage (PIV). This is the largest amount of reverse-bias voltage the diode’s junction can withstand for an indefinite period of time. If a reverse voltage exceeds this level, the voltage will “punch through” the depletion layer and allow current to flow backward through the diode (secondary breakdowns, which usually destroy the diode.  Diodes must have a peak inverse voltage rating that is higher than the maximum voltage that will be applied to them in a given application i.e PIV rating ≥ V_m
4. Maximum power dissipation:- The actual diode power dissipation (Watts) is calculated by multiplying the forward voltage drop and the forward current.