| 摘要 |
PURPOSE:To attain stable characteristic with less variation of the gain control characteristic by changing a current of a current source or a resistor of an emitter resistor circuit whose emitters are connected in common in a couple of differential amplifier transistors (TR) in response to the control input. CONSTITUTION:Collectors of differential amplifier TRs Q1, Q2 are connected to differential output terminals 13, 14, to a VCC power supply terminal via load resistive elements R1, R2 and a resistive element R3 is connected between the emitters. The collector and base of the TRs Q3, Q4 are connected together and the emitters are connected mutually to form a differential pair. Then the connecting point between the emitters is connected to common via a variable current source 11 whose current is controlled in response to the control input and the collectors of the TRs Q3, Q4 are connected to the emitters of the TRs Q1, Q2 correspondingly. In changing the equivalent emitter resistance between the emitters in response to the control input, the TR forming part of the equivalent emitter resistor is operated at the non-saturation region.
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