the auxiliary transistor 602 _ x is electrically connected to a base of the amplifying transistor 600 _ x note that in the power amplifier 60 a number of the auxiliary transistors 602 _ 1 602 _n is the same as a number of the amplifying transistors 600 _ 1 600 _n and gates of the auxiliary transistors 602 _ 1 602 _n are combined together nevertheless it is not limited thereto for example fig7 is a schematic diagram of a power amplifier 70 according to an embodiment of the present invention the power amplifier 70 comprises amplifying transistors 700 _ 1 700 _n and auxiliary 702 _ 1 702 _ 3 gates of the auxiliary transistors 702 _ 1 702 _ 3 respectively receive bit controlled signals bit_ 1 bit_ 3 generated by a control circuit 706 to control on off statuses of the auxiliary transistors 702 _ 1 702 _ 3 as long as drains of the auxiliary transistors 702 _ 1 702 _ 3 are coupled to collectors of the amplifying transistors 700 _ 1 700 _n and sources of the auxiliary transistors 702 _ 1 702 _ 3 are electrically connected to bases of the amplifying transistors 700 _ 1 700 _n requirements of the present invention are satisfied in summary the power amplifier.