there is shown a circuit diagram of a power amplifier circuit according to another embodiment of the present invention as shown in figure the power amplifier circuit 304 of the present embodiment further comprises an output power detection unit 38 the output power detection unit 38 comprises one or two third transistors 381 when the number of the third transistor 381 is two these two third transistors 381 will be able to form as a differential pair of third transistors the third transistors 381 are provided with the first terminals connected to the power supply voltage v dd the second terminals with a second current i 2 and connected to the second terminals of the first transistors 331 and the control terminals connected to the first terminals of the second transistors 351 via a third capacitor 383 to receive the single rf output signal or the differential pair of output signals rf_outn and rf_outp the output power detection unit 38 is used for detecting the power of the output signals rf_outn and rf_outp to generate a second detection signal s d2 at the second terminals of the third transistors 381 furthermore the control terminals of third transistors 381 are connected together via a fourth load element 384 in each embodiment of the present invention the first load elements 334 the second load elements 354 the third load elements 355 or the fourth load elements 384 are resistor or inductor further referring to fig8.