| 摘要 |
PURPOSE:To reduce noises of a gain control circuit greatly by providing transistors (TR), supplied with gain control signals, in differential form, and connecting load TRs for them on emitter-follower basis. CONSTITUTION:Transistor TRs 9 and 10 supplied with gain control signals are connected in differential form. As loads on those TRs 9 and 10, TRs 7 and 8 applied with a constant voltage at bases are connected on emitter-follower basis. Further, the emitter voltages of the TRs 7 and 8 are applied to the bases of TRs 3 and 4 which constitute a differential amplifier supplied with an input signal. When the gain control signal is applied to the base of the TR9 or TR10, its variation is detected by the TRs 7 and 8 to perform gain control. Thus, a gain control circuit is formed to reduce its noises greatly. |
