Abstract: An integrated circuit device includes a power amplifier having an FET; a negative voltage generator for supplying a negative voltage to the power amplifier; a power supply terminal receiving a positive power supply voltage through an external switch and applying the positive power supply voltage to the negative voltage generator and, through an internal switch, to the power amplifier; and a negative voltage detector for detecting the negative voltage output from the negative voltage generator and sending a control signal to the internal switch so that the internal switch is closed when the output voltage from the negative voltage generator is lower than a threshold negative voltage and open when the output voltage is higher than the threshold negative voltage. It is not necessary to supply an external negative voltage as a gate bias voltage of the FET.