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A PiN diode has a large intrinsic region that slows down voltage. It is used as an RF switch, in photovoltaic cells, and as an emergency shunt for power overloads. Doping creates variable areas in the semiconductor.
A PiN diode is a type of diode that contains a semiconductor with a very large intrinsic region (the “i”) between a positive and a smaller than normal negative region (the “P” and the “N”). This large neutral region in the center of the semiconductor will reduce the rate at which voltage moves through the system. A PiN diode is used for three basic reasons: as a radio frequency (RF) switch, as part of a photovoltaic cell, and as an emergency shunt for power overloads.
A typical diode has a very small intrinsic area. Usually, diodes consist of two connection terminals connected by a semiconductor. Diodes absorb energy through an anode and release it into a positively charged area of a semiconductor. A small intrinsic layer separates the positive area from a negative region. Power travels through the intrinsic into the negative and then through a cathode into the device.
A PiN diode works a little differently. Power enters the diode and transfers normally to the positive region, but then affects an extremely large intrinsic area. This area acts like a dam for the power moving through the system. It fills with more and more power as the positive area keeps sending it. When it finally fills up to the point where it simply can’t take any more, it starts pushing the power into the negative zone.
These variable areas in the semiconductor of the PiN diode are created through a process called doping. Most semiconductors are made of silicon. When the actual semiconductor is built, the silicon is infused with a variety of metals, some of which enhance the positive system, while others enhance the negative. The intrinsic area on the PiN diode is doped very lightly if at all. This causes power to pour into it and then sit as the current builds, then rushes out.
When used as part of an RF switch, a PiN diode isolates signals. The construction of the diode allows some signal types to move through the intrinsic area more easily than others. This allows specific signals to pass while keeping others permanently blocked.
Photovoltaic cells require bursts of energy to operate. In this case, the PiN diode prevents power from entering the system until a large buildup occurs. That power is released all at once, activating the cell.
The last common use for a PiN diode is as an emergency power shunt. As power travels through a system, a secondary drop may contain a PiN diode connected directly to the device’s system ground. If the device is operating normally, the PiN’s intrinsic area never fills up and, therefore, never moves power. If a surge hits the device, the intrinsic area fills up and current moves from the device to ground, hopefully before the device is damaged.
