Bias control circuit

A bias control circuit for controlling a bias current of a high-frequency power amplifier, comprising:

• a voltage conversion circuit for receiving a control voltage and for converting the control voltage into a bias control voltage to be supplied to the high-frequency power amplifier, said voltage conversion circuit includes:
• a two-stage differential amplifier, constituted by two pairs of amplifying transistors and having an inverting input terminal, a non-inverting input terminal, an inverting output terminal and a non-inverting output terminal, for receiving the control voltage at the inverting input terminal and for outputting an inverting output voltage and a non-inverting output voltage from the inverting output terminal and the non-inverting output terminal, respectively;
• an output transistor for effecting low impedance conversion for the non-inverting output voltage of the two-stage differential amplifier to obtain an output voltage and for outputting the thus obtained output voltage, as the bias control voltage, to the high-frequency power amplifier;
• a feedback circuit for making entire feedback of the output voltage to the non-inverting input terminal of the two-stage differential amplifier and for making feedback of the inverting output voltage of the two-stage differential amplifier to the inverting input terminal thereof;
• and
• a diode-connected biasing transistor for regulating base voltages of the pair of amplifying transistors constituting a first amplifier stage of the two-stage differential amplifier.