POWER AMPLIFICATION SYSTEM AND MOBILE RADIO COMMUNICATION TERMINAL

摘要

A power amplification system having a high-frequency power amplifier circuit section (10) which uses source-grounded enhancement type n-channel MESFETs J1 and J2 as the amplifier elements, is supplied with a drain bias voltage Vdd and a gate bias voltage Vgg of O V or a low positive value from a power source having a single polarity, and outputs input signals inputted in a state where the signals are superposed upon the voltages Vdd and Vgg as the changes in drain currents Id1 and Id2 after amplification, an output matching circuit section (11) which outputs the amplified high-frequency signals after impedance matching, and a gate bias voltage circuit section (12) which supplies a gate bias voltage to the circuit section (10); and a mobile radio communication terminal incorporating the system. In the MESFETs J1 and J2, the value of a forward DC gate voltage at which the gate current per 100- mu m gate width exceeds 100 mu A reaches at least 0.65 V when the DC gate voltage is applied in the forward direction across the gate terminals of the MESFETs J1 and J2 by grounding the source terminals thereof.