| 摘要 |
PURPOSE:To decrease the current consumption by connecting a common emitter of a 4th differential pair to a 2nd differential pair so as to eliminate the need for a constant current source which has been required in a conventional circuit for the 4th differential pair in a gain control circuit where the 1st and 2nd control voltage are impressed respectively to the 1st, 2nd and the 3rd, 4th differential pairs. CONSTITUTION:A voltage current conversion circuit (comprising a transistor Q9 and a resistor R1) converting an input signal VIN into a current, the 1st differential pair comprising TRs Q1, Q2, the 2nd differential pair comprising TRs Q3, Q4, the 3rd differential pair comprising TRs Q5, Q6, the 4th differential pair comprising TRs Q7, Q8 and a constant current source (comprising a TR Q10 and a resistor R2) are provided. Thus, the gain control to an input signal is attained by using two control voltages impressed to terminals 1A, 1B and 2A, 2B the same as a conventional gain control circuit, and also the current consumption being thrice the DC current corresponding the DC component of the input signal in the conventional circuit is reduced to that twice the DC current corresponding thereto.
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