| 摘要 |
PURPOSE:To start up a DC feedback type amplifier gradually and to prevent a shock noise from being generated by interposing between a bias point for determining the current gain of the DC feedback type amplifier and a reference potential point where a capacitor is connected, and turning on the diode when a current is impressed and shunting a bias current. CONSTITUTION:When a power source is turned on, constant current sources 26 and 27 generate output currents immediately and the capacitor 25 begins to be charged with the output current of the constant current source 26. The capacitor 25 is not charged right after the power source is turned on, so the potential Vref at a point A falls to zero and the diode 28 turns on, so that the output current of the constant current source 27 is shunt by the diode 28 and flows in the capacitor 25. When the reverse saturation current of a bias transistor (TR) 24>> the reverse saturation current of the diode 28, the current flowing through the TR 24 right after the power source is turned on is cased. The current flowing through the TR 24 increases as the Vref increases, and currents flowing through constant current TRs 13-21 also increase correspondingly. Then when the Vref increases sufficiently, the diode 28 turns off and the current flowing to the constant current source 27 all flows to the bias TR 24.
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