| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable gain amplifier circuit the current of which is reduced when a voltage gain is dropped and which exhibits no essential deterioration in a distortion characteristic. SOLUTION: The bases of bipolar transistors Q1, Q3, Q5, Q2, Q4 and Q6 constituting a plurality of emitter ground amplifier circuits are connected together. Switches SW2, SW1 and SW0 are arranged on the emitter sides of the bipolar transistors. The switches SW2, SW1 and SW0 are changed over and the emitter sides are made to ground potential gnd. Thus the emitter ground amplifier circuit having a different voltage gain is selected so as to control the voltage gain. Different values are given to a collector current I0 and emitter resistance Re between the emitter ground amplifier circuits, and the ratio of the collector current I0 is set to be in inverse proportion to the ratio of emitter resistance Re. Consequently, the collector current I0 decreases when the voltage gain is dropped, and deterioration of the distortion characteristic can substantially be eliminated. COPYRIGHT: (C)2004,JPO&NCIPI
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