| 摘要 |
PURPOSE:To make stable the output DC voltage of the preamplifier and to obtain the circuit easy for circuit integration, by using the differential amplifying circuit and giving the bias voltage stably to the first stage transistor. CONSTITUTION:Transistor TrT1 is connected to the differential amplifying circuit constituted with TrT2 and T3, and the bias voltage is fed with the resistor R3. Further, the input VIN is amplified with TrT1 and is further amplified with the differential amplifier constituted with TrT4 and T5 and output Vout is made via TrT6. In the amplifier thus constituted, the bias voltage of TrT1 is always stable, and the collector voltage is almost equal to the stable voltage E1 independently of the dispersion of amplification factor and it is stable even with the amplification factor varied. Accordingly, the output of TrT1 is connectable for DC coupling to the next stage, then circuit integration is made easy. Further, the differential amplification circuit consisting of TrT4 and T5 can be operated in the condition of linear operation independently of the variation of the amplification factor of TrT1. |
