| 摘要 |
PURPOSE:To keep a DC component of output current constant independently of the variation of power supply voltage by supplying a current corresponding to the current of a control means for setting the potential of an output terminal to about a half of a power supply voltage at the time of no input to a voltage output terminal of an amplifier. CONSTITUTION:A bias voltage from a bias voltage generating circuit 11 and an input signal from a signal source 13 are supplied to the base of a TRQ3 of a differential amplifier circuit 12. An amplifier circuit 15 is driven by the output of the circuit 12 and a feedback signal from a feedback circuit consisting of resistors R2, R3 and a capacitor C2 is supplied to the base of a TRQ4 in the circuit 12. A current is supplied to the circuit 15 so that the potential of a voltage output terminal B point of the circuit 15 becomes about a half of the power supply voltage Vcc under the control of a control circuit 17 at the time of no input. Simultaneously, a current corresponding to the output current of the circuit 17 is supplied to an output terminal B by a TRQ12 of which base is connected to the bases of TRQ10, TRQ11 of the circuit 17 and a control circuit 19 consisting of TRs Q13, Q14, so that the DC component of an output from a terminal 16 is kept constant even if the power supply voltage Vcc is varied. |
