Radio amplifier with output filter - has real input impedance to reduce distortion caused by intermodulation

摘要

The amplifier is used in a radio receiver. It has a frequency-dependent output impedance to reduce distortion caused by intermodulation. There is a coupling circuit with an approximately constant real input impedance which acts as a load to the amplifier. The frequency-dependent output impedance may consist of a filter whose input impedance is real at the resonant frequency of the filter. A parallel-resonant circuit is coupled in parallel with the output of the amplifier.