OUTPUT POWER DETECTOR FOR HIGH FREQUENCY POWER AMPLIFIER

PROBLEM TO BE SOLVED: To improve detection sensitivity in an area where the low output level of an amplifier is low, and to reduce the effect of output impedance upon a detection output, in a high frequency power amplification circuit of a multi-stage configuration wherein a plurality of power amplification transistors is cascaded. SOLUTION: Inputs of amplification stages in multi-stage power amplification transistors are defined as detection inputs, peak hold detection is performed, respectively, an output voltage compared with a reference signal is converted into a current, and detection outputs of the stages are summed up, thereby the linearity of the detection output is improved. Thus, since detection sensitivity is improved even in the case that the output level of the amplifier is low, it controllability of the power amplifier can be improved. Furthermore, since the output of the power amplification circuit is not defined as detection input, it becomes possible to reduce the effect in the case that the output impedance is varied. Moreover, temperature dependency and power supply voltage dependency can be reduced. COPYRIGHT: (C)2008,JPO&INPIT