| 摘要 |
PURPOSE:To eliminate the consumption of the bias current of an amplifying circuit except when the class ''A'' amplification of an AC signal is performed, and to save electric power by applying the slow varying voltage of the integrating circuit of a control system to the base of the transistor (TR) of a bias current controlling circuit. CONSTITUTION:An intermittent signal from an input terminal T1 is applied to a TRQ2 which inputs the output of the integration circuit and a specified voltage is supplied from a voltage source B to the emitter of the TRQ2; the specified voltage is equalized to the voltage developed across a resistance R19 when a specified bias current flows through a TRQ3. This specified voltage is inputted to the operational amplifier A of the bias current controlling circuit through a diode D2 and the output voltage of the integration circuit is inputted to the amplifier A through a resistance R10. When the intermittent signal drops to a low level, the diode D2 is cut off until the output voltage of the TRQ3 attains the specified voltage and the base voltage of the TRQ3 is raised; when the output voltage of the integration circuit exceeds the specified voltage, the diode D2 is turned on to eliminate the current except when the amplifier A amplifies the output of an oscillator OSC. |
