TRANSMISSION CIRCUIT AND ITS METHOD

摘要

PROBLEM TO BE SOLVED: To bypass-control a power amplifier without increasing the current of a circuit. SOLUTION: A first switch circuit 103 changes over an input signal to either of two routes. A signal outputted to one route with the change-over is amplified by a power amplifier 102 and is outputted to a circulator 106. A second switch circuit 104 cuts the first switch circuit 103 and the circulator 106 at the time of amplifying the input signal and terminates the circulator 106 through a fixed resistor 111 corresponding to the characteristic impedance of a circuit. A signal outputted to the other route from the first switch circuit 103 is outputted to the circulator 106 when the input signal is not amplified. A third switch circuit 105 turns on the drain power 109 and the gate power 110 of the power amplifier 102 only at the time of amplification.