| 摘要 |
PURPOSE:To attain linear gain control by applying feedback control to the titled circuit so that the sum of collector currents of both transistors (TR) is made coincident with a control value in an amplifier using emitters of both the TRs as an input and collectors as an output. CONSTITUTION:Differential inputs Is, -Is and a bias I0 are given to input terminals 1, 2, currents I3, I4 flowing TRs Q3, Q4 flow both to a resistor R3, and the currents I3, I4 and currents I1, I2 are proportional. Then the component of the signal Is is cancelled from the sum of the currents I3, I4, the result is proportional to the bias current and the feedback control is applied so that the voltage produced from the bias current is equal to a control voltage E1. Thus, the gain is changed linearly to the control voltage E1.
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