| 摘要 |
The present invention provides a power supply circuit, which supplies a power supply voltage to a high frequency power amplifier. The power supply circuit comprises a DC-DC converter, a voltage control transistor, and a control circuit which controls the voltage control transistor. When the power supply circuit is used in a CDMA-system cellular phone, the power supply circuit supplies a power supply voltage generated by the DC-DC converter to the high frequency power amplifier upon a low output, whereas upon a high output, the power supply circuit turns on the voltage control transistor to directly supply a battery voltage to the high frequency power amplifier. On the other hand, when the power supply circuit is used in a CGS-system cellular phone, the power supply circuit supplies a power supply voltage generated by the DC-DC converter to the high frequency power amplifier, whereas upon a high output, the voltage control transistor is controlled by the control circuit based on a signal for designating an output level to generate a power supply voltage supplied to the high frequency power amplifier.
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