Application Note: A Low Distortion PIN Diode Switch Using Surface Mount Devices

One of the practical applications of the surface mounted PIN diode is in the design of low current, low cost RF switches. In the design of such circuits, the diode is generally treated as a current controlled ideal resistor which is switched between low resistance and high resistance states.

However, the PIN diode has some important second order non-linear characteristics which can give rise to the generation of harmonic and intermodulation distortion in switching circuits, particularly those which employ high RF power. A low distortion SPDT switch, using a new type of PIN diode designed specifically for low distortion performance, is described.

All circuits which contain non-linear elements such as diodes and transistors produce certain kinds of distortion to various degrees.