Bandpass filter circuit for mobile radio communications device - has input signal switched between inputs of at least 2 parallel bandpass filters via preceding IC device

摘要

The bandpass filter circuit has at least 2 bandpass filters (1,2) with their outputs coupled together to provide the circuit output (3), which are preceded by an IC device (7) with respective signal paths (41,51) for each of the bandpass filters, coupled to a control circuit (6), for switching the input signal to one or other of the bandpass filters. Each of the signal paths may have an output stage (4,5), e.g. having a difference amplifier and an emitter follower, with its supply current feed (61,62) selectively switched on or off by the control circuit.