| 摘要 |
PURPOSE:To reduce S/N without changing distortion factor, by constituting the circuit with two differential amplifiers, current Miller circuit, voltage-current conversion circuit and current-voltage conversion circuit. CONSTITUTION:A current Miller circuit 24 being a common load is connected to differential amplifiers 22, 23. A voltage-current conversion circuit 26 which changes common emitter currents i1, i2 of the amplifiers 22, 23 in opposite phase according to the input signal fed to input terminals 25a, 25b, is connected to a common emitter circuit to the amplifiers 22, 23. Further, an output voltage V0 is obtained from a connection point 27 between the amplifiers 22, 23 and a circuit 24 via a current- voltage conversion circuit 28. With such circuit constitution, the output voltage V0 is proportional to an input voltage Vi, and the gain is determined with the exponential function of a control voltage given to the terminal 35. When the control voltage is increased and the gain is decreased, the collector currents i3, i4 of transistors 29, 33 are decreased, resulting that noise voltage is made smaller. |
