Diode Applications

1.) Rectifier
A rectifier is a device that changes AC to DC.

It is a process by which alternating current is changed to direct current. Since diodes conduct in only one direction, they serve as rectifiers.

2.) Detector

A diode detector in an AM receiver recovers the original information from the AM transmitter.

3.) Half wave rectifier diagram

 

During the positive half cycle of the AC supply, the diode is forward biased and it conducts. This signal is thus present at the load.

During the negative half cycle of the AC supply, the diode is reversed biased and it does not conduct.

 

Thus throughout the negative half cycle there is no signal present at the load. Therefore the signal output of load appears to be shown as follows:

 

Average value, is the value you would measure on a DC voltmeter.

 

Vp is the peak value of the voltage.

4.) Peak Inverse Voltage (PIV)
Occurs at the peak of negative cycle alternation of an AC input when the diode is reverse biased.

It is define as the maximum reverse bias voltage that can be applied to a diode without the diode breaking down. PIV equals the peak value of input (reverse) voltage before going through the diode.

The diode must be capable of withstanding this amount of repetitive reverse voltage.

5.) Summary
The table below shows the maximum ratings for a certain series of rectifier diodes.

These are the absolute maximum values under which the diode can be operated without damage to the device.

The greatest reliability, the diode should always be operated well under these maximums.

Generally the maximum ratings are specified at 25 degree Celsius and must be adjusted downward for higher temperatures.