PIN Diode Applications & Circuits
- a summary of the various PIN diode applications and the types of PIN circuits used.
The PIN diode is used in a variety of different applications from low frequencies up to high radio frequencies. The properties introduced by the intrinsic layer make it suitable for a number of applications where ordinary PN junction diodes are less suitable.
In the first instance the diode can be used as a power rectifier. Here the intrinsic layer gives it a high reverse breakdown voltage, and this can be used to good effect in many applications.
Although the p-i-n diode finds many applications in the high voltage arena, it is probably for radio frequency applications where it is best known. The fact that when it is forward biased, the diode is linear, behaving like a resistor, can be put to good use in a variety of applications. It can be used as a variable resistor in a variable attenuator, a function that few other components can achieve as effectively. The PIN diode can also be used as an RF switch. In the forward direction it can be biased sufficiently to ensure it has a low resistance to the RF that needs to be passed, and when a reverse bias is applied it acts as an open circuit, with only a relatively small level of capacitance.
Another useful application of the PIN diode is for use in RF protection circuits. When used with RF, the diode normally behaves like a resistor when a small bias is applied. Hover this is only true for RF levels below a certain level. Above this the resistance drops considerably. Thus it can be used to protect a sensitive receiver from the effects of a large transmitter if it is placed across the receiver input.
Finally the PIN diode finds many applications as a photodiode, although this will be explained separately.
By Ian Poole
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