| 摘要 |
PURPOSE:To widen the gain variable width without increasing the circuit current by changing simultaneously a current flowing respectively to the 1st and 2nd differential amplifiers. CONSTITUTION:A prescribed gain control voltage VC is fed between bases of transistors (TRs) Q5, Q6 from a gain control variable voltage source 12 in a current sharing circuit 3. As a result, a collector current in response to the said control voltage VC flows as currents I1, I2 of differential amplifiers 1, 2 of the 1st and next stages respectively. The current flowing through the differential amplifiers 1, 2 of the 1st and next stages is set optionally from I1=I0, I2=0 to I1=0, I2=I0 by using the control voltage VC optionally. Although the current I1 is to be increased as the gain is decreased and the gain is not make zero in a conventional circuit, the titled circuit offers the zero gain with I1=I0 and I2=0 and the circuit current is always constant (=I0).
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