| 摘要 |
PURPOSE:To determine a gain clearly by a control voltage over the wide dynamic range of (n+2) stages of variable gain amplifiers and to realize requested characteristics by providing a differential amplifier for control voltage conversion to the differential amplifier or a gain control circuit. CONSTITUTION:The 1st differential amplifier of the gain control circuit consists of transistors(TR) Q1-Q6; a DC control voltage V2 is applied to the 1st input couple and the output of the differential amplifier for control voltage conversion which consists of TRs Q7 and Q8 is supplied to the 2nd input couple. The collector voltage of this TRQ7 is determined by a current I1 and a resistance R4 and made constant, and the variable range of a voltage V02 is specified from 0 to R3.I1. The output voltage of the 1st differential amplifier is divided by resistances R5-R8 respectively and applied as a voltage V20 to the input couple of TRs Q15 and Q16 constituting the 2nd differential amplifier. Further, an AC signal VIN is applied to the 1st input couple of the 2nd differential amplifier and the AC signal level of the output voltage V from TRs Q11-Q14 is determined clearly by the control voltage V2 to realize the requested characteristics easily. |
