| 摘要 |
PURPOSE:To make the base current of a main transistor (TR) constant, by providing a control TR which detects and switches the variance in the base current fed to a main TR via a driving TR from a DC power supply. CONSTITUTION:The base current of a main transistor TR2 is fed from a DC power supply 1 via a driving TR3 and returns to the power supply 1 via a current detecting resistor 9. The driving TR3 is conductive by an output I1 of a driving signal circuit and TR2 is conductive with a driving base current I4 to be flowed. When the DC power supply 1 is in variance, the potential across the resistor 9 is increased, and when it exceeds a voltage between the base and emitter of a control TR8, the TR8 is conductive to flow a current I3, and a base current I2 of the TR3 is I2=I1-I3, resulting that the current I2 is decreased and the current I4 is always at a constant current when the I4 is going to increase. A current I5 flows from a driving signal circuit in the emitter base direction to turn off the main TR2. Thus, the base current of the main TR2 can be made stable with a simple constitution. |
