| 摘要 |
PURPOSE:To obtain a constant-voltage circuit which is small in required voltage drop between the input and output, by connecting an input terminal to the emitter of a transistor and an output terminal and voltage dividing resistance to the collector, respectively and impressing an error amplified output between a voltage divided value and reference value on the base of the transistor. CONSTITUTION:An input terminal 1 is connected to the emitter of a pnp transistor (TR)7 and an output terminal 2 is connected to the collector, and then, an earth is connected to the base through a resistance 8. An output voltage VOUT is divided in terms of voltage by means of voltage dividing resistances 5 and 6 and the divided voltage is impressed on the (+) input of an error amplifier 4. A reference voltage Vref from a reference voltage generator 3 is impressed on the (-) input of the amplifier 4 and the output of the amplifier 4 is impressed on the base of the TR7 through a resistance 9. When the divided voltage of the voltage VOUT becomes higher than the voltage Vref, the output of the amplifier 4 becomes higher and the voltage between the base and emitter of the TR7 decreases and the collector current is reduced, and therefore, the output voltage is maintained at a constant level. Since the TR7 makes normal operation when the voltage across its collector and emitter is higher than a saturation voltage (about -0.2V), a prescribed constant voltage is outputted stably even when the voltage difference between the input and output is small. |
