Rectifier diode can make use of the unidirectional conductivity of PN junction to change alternating current into pulsating direct current. It is mainly used for various low-frequency half wave rectification circuits. If full wave rectification is required, it shall be connected into a rectifier bridge.

Characteristics of rectifier diode:

1. Positive

When a forward voltage is applied to the rectifier diode, the forward voltage in the starting part of the forward characteristic is very small, which cannot effectively overcome the blocking effect of the electric field in the PN junction. When the forward current of the rectifier diode is almost zero, this section is called the dead zone, and the forward voltage that cannot make the diode turn on is called the dead zone voltage.

When the forward voltage of the rectifier diode is greater than the dead time voltage, the electric field in the PN junction is effectively overcome, the forward conduction of the rectifier diode is on, and the current rises rapidly with the increase of the voltage. In the normal current range, the rectifier diode terminal voltage is almost unchanged when conducting.

2. Reversibility

When the applied reverse voltage of the rectifier diode does not exceed a certain range, the reverse current formed by the drift movement of a few carriers of the current through the rectifier diode. Because the reverse current of the rectifier diode is very small, the rectifier diode is in the off state. The reverse saturation current of rectifier diode is affected by temperature.

In general, the reverse current of silicon rectifier diode is much smaller than that of germanium rectifier diode. The reverse saturation current of small power silicon rectifier diode is in the order of nA, and the reverse saturation current of small power germanium rectifier diode is in the order of nA μ A Order of magnitude. When the rectifier diode temperature rises, the semiconductor is thermally excited, and the number of minority carriers will also increase.