The most common function of a diode

The most common function of a diode is to allow current to pass in one direction (referred to as the forward direction of the diode), while preventing current from passing in the opposite direction (reverse direction). In this way, the diode can be viewed as an electronic version of the check valve. This unidirectional behavior is called rectification, which is used to convert alternating current (AC) into direct current (DC). The form of rectifier and diode can be used for tasks such as extracting modulation from the radio signal in the Radio receiver.

However, due to the nonlinear current voltage characteristics of diode, their behavior may be more complex than this simple switching action. Only when there is a certain threshold voltage or cut in voltage in the forward direction (the diode is referred to as a forward biased state), does the semiconductor diode begin to conduct electricity. The voltage drop at both ends of the forward bias diode varies only slightly with current and is a function of temperature. This effect can be used as a temperature sensor or reference voltage. In addition, when the reverse voltage at both ends of the diode reaches a value called breakdown voltage, the high resistance of the diode to reverse flow suddenly drops to low resistance