Selective RF circuit with varactor tuned bandpass switched bandpass filters

摘要

A selective RF circuit for a double conversion tuner includes three double tuned bandpass circuits, each of which is tunable over approximately one-third of the tuning range. Switching diodes are used at the input and the output of each of the bandpass sections for selectively activating one of the bandpass sections and deactivating the remaining ones in response to a bandswitching signal. Operational amplifiers or other devices supply the input and output switching diodes by providing a current sink for the active bandpass and current sources for the inactive bandpasses.