| 摘要 |
PURPOSE:To decrease the lower limit of a power supply voltage by connecting a collector of the 1st stage transistor (TR) of Darlington connection in a control circuit to an emitter of a TR of the next stage via a resistor and a DC power supply. CONSTITUTION:The collector of the 1st stage TR 5-1 of Darlington connection is connected to the negative side of a DC power supply via a resistor 5-3. When a power supply voltage drops, an output of a high frequency power amplifier 1 is decreased, then a detection voltage obtained by a detection circuit 2 is lowered and the difference with a reference voltage in the DC amplifier 3 is increased. Thus, a base current of TRs 5-3, 5-2 is increased to decrease the difference, then the voltage drop of the part is decreased and a DC voltage fed to the high frequency power amplifier circuit 1 is increased to increase the high frequency power, thereby keeping the power constant. Thus, the lower limit of the power supply voltage is decreased. |
