| 摘要 |
PURPOSE:To design an automatic control circuit having an excellent characteristic by extracting an output from a collector terminal of an amplifier of differential connection and applying a control voltage to its base. CONSTITUTION:An input terminal of the amplifier comprising transistors(TRs) TR3, TR4 of differential connection is denoted as (a) and an output terminal is denoted as (d) in the Figure. The output terminal (c) leads to the collector of the TR3. An output of the terminal (c) is applied to a base terminal (g) or (h) of TR9, TR10 constituting a differential amplifier via a suitable amplifier 100 and a rectifier circuit 200. A change in the control voltage caused by the TR9, TR10 is applied to the TR3, TR4 as a change in the base-emitter voltage of emitter follower TR7, TR8. Then, a signal current flowing to a load resistor R15 is changed for attaining the gain control. Thus, the automatic gain control circuit with good S/N is formed. |
