PIN Diode Fundamentals and Applications

The PIN diode is a common microwave semiconductor device used in various applications. This page will cover the fundamentals of PIN diodes and their practical uses.

Unlike a standard PN junction diode, a PIN diode incorporates an insulating layer between the P-type and N-type materials. This unique structure distinguishes it from its PN junction counterpart.

The “I” region in a PIN diode is a lightly doped N-type region.

When a forward bias is applied, charge carriers are injected into this insulating layer from both the P and N regions.

Due to the light doping in the I-layer, a small number of charge carriers remain uncombined. This results in very low resistivity in the insulating region.

PIN Diode Applications

PIN diodes find applications in RF delay lines, phase shifters, and amplitude modulators.

One common use is as a switch in transceiver systems. The figure below illustrates how a PIN diode can be used to switch between transmit and receive operations using a single antenna.

The switch position determines whether the antenna is used for transmitting or receiving.