Abstract: A transmission output circuit can always perform correct transmission power control, and can detect the abnormality of transmission power, which interferes with other users, and part troubles, which cause erroneous transmission. The transmission output circuit includes transmission power control data generation means for generating a gain control signal for performing the feed forward control of gain control amplification means in order that the output signal level of the power amplification means may be a target transmission power output level, detection means for detecting the output signal of the power amplification means to obtain detected signal data, and judgment means for judging the existence of the occurrence of trouble in the transmission output system by using the detected signal data from the detection means.