| 摘要 |
PURPOSE:To obtain a gain control circuit suitable for IC-inplementation by applying a control voltage to the base of one of two bipolar transistors (TR) connected in series, and thus varying the base resistance of the other TR. CONSTITUTION:A signal Vi inputted to a terminal 6 is amplified by a TR1 and then inputted to the base of a trailing TR4. A collector current flowing through the TR4 varies with a control voltage VAGC applied to the base of a TR3 whose collector is connected to the emitter of the TR4. The internal base resistance of the TR4 varies with the collector current of the TR3. In general, the internal base resistance of a bipolar TR decreases by one-two digits by clouding effect as the collector current increases. As a result, the gain is controllable. This circuit is formed only by bipolar technique. |
