| 摘要 |
PURPOSE:To reduce the dynamic range as an input stage which is used to transmit the signal to a control circuit part, by securing the dynamic range to the input signal with use of a PNP transistor differential amplifier having an active load. CONSTITUTION:The constant current source of a diode D8 plus transistors Q10 and Q11 applies the DC current to differential amplifiers Q12 and Q13, and the input signal S1 has no relation with the current source. And the DC voltage required at that pat is set nearly at 0.75V. On the other hand, the collectors of the Q12 and Q13 drive active diodes D6 and D7 by the current. Thus the forward voltage of the D6 and D7 is enough with about 0.75V. Accordingly the voltage that is available for the differential amplifiers Q12 ans Q13 is shown as VCC- (VDS+VD6)=TCC-1.5V, and a margin is obtained for the voltage by an amount equivalent to the differential voltage. The voltage obtained by subtracting the base-emitter voltage of the Q12 and Q13 from the differential voltage is equal to the dynamic range to the signal S1. |
