A High Power Protector Using PIN Diodes

PIN diodes are useful in high power switching applications because their microwave impedance is essentially a controllable conductance in shunt with a nearly constant capacitance. The diodes are made by diffusing heavily doped N+ and P+ layers into a /spl pi/-type body. When reverse biased the R. F. impedance is determined by the /spl pi/-region capacitance in series with a small resistance. If a forward bias current is applied, the /spl pi/-region is progressively filled with carriers and the device becomes a conductance increasing to a maximum value of about 10 mhos . It is this high conductance which accounts for the high power rating of PIN diodes.