DUAL BAND CELLULAR PHONE WITH TWO POWER AMPLIFIERS AND POWER CONTROL CIRCUIT THEREFOR

摘要

A transmitter for a cellular phone comprising an antenna and being operable at a first radio frequency band and a second radio frequency band is disclosed. The transmitter comprises a first power amplifier and a second power amplifier, one of which is active at a time. The first power amplifier has an input for a first signal at the first radio frequency band, an input for a first control signal and a first output for an amplified first signal. The first output is connectable to the antenna. The second power amplifier has an input for a second signal at the second radio frequency band, an input for a second control signal and a second output for an amplified second signal. The second output is connectable to the antenna. The transmitter further comprises a single control module associated with the first and second outputs of the power amplifiers. The control module generates a control signal for the active power amplifier. The control signal forms part of a feedback control loop, and is a function of the amplified signal output from the active power amplifier and a reference signal which defines a desired characteristic of the amplified signal.