| 摘要 |
A variable gain amplifier circuit is provided so that an electric current decreases when a voltage gain is lowered and that the amplifier circuit is substantially free of a deterioration in distortion characteristics. The bases of bipolar transistors Q 1 , Q 3 and Q 5 and the bases of bipolar transistors Q 2 , Q 4 and Q 6 are connected in common with each other, these bipolar transistors forming a plurality of common-emitter amplifier circuits, and switches SW 2 , SW 1 and SW 0 are connected to the respective sides of the bipolar transistors. The emitter sides are held at a ground potential gnd by switching the switches SW 2 , SW 1 and SW 0 so that the voltage gain is controlled by selecting the common-emitter amplifier circuits different in voltage gain. A collector current I 0 and an emitter degeneration resistance Re between the common-emitter amplifier circuits are so arranged as to have different values. The ratio of the collector current I 0 is set inversely proportional to the ratio of the emitter degeneration resistance Re, whereby the collector current I 0 decreases when the voltage gain is lowered and a deterioration in distortion characteristics is substantially obviated.
|
