| 摘要 |
PURPOSE:To reduce the ripple of a smoothing power supply by permitting other transistor to turn off the base current of a transistor when the transistor is reversely biased to attain a potential to work as a reverse transistor. CONSTITUTION:AC signals are superimposed to line terminals L1-L2. If the line terminal L1 falls below a constant voltage Vcc, the potential of the base of a transistor Q3 drops and the Q3 is turned on. The potential of the emitter of the Q3, one side of an R2 and the emitter of a transistor Q1 fall, and the Q1 and Q2 are turned off. The current of a constant-current circuit 1 flows through the Q3 and the constant-current circuit 1 is not saturated. The potential of the emitter of the transistor Q1 falls, and its potential relation comes to that the Q1 works as the reverse transistor. The base current of the Q1 does not flow since the transistor Q2 is turned off, whereby the Q1 does not work as the reverse transistor, and discharge from the power supply Vcc through the Q1 is eliminated. Thus, the current deficiency of a constant voltage circuit 3 does not occur, and the impedance of the constant voltage circuit 3 is held low, whereby ripple decreases.
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