| 摘要 |
PURPOSE:To provide a gain control circuit advantageous to miniaturization and light weight of a portable telephone set, long talking time and cost reduction. CONSTITUTION:A circuit is provided with a source grounded dual gate FET 40 and a transistor(TR) 61 of emitter follower. First and second elements 63, 64 connected in series are provided between the emitter of the TR 61 and a voltage source -VEE opposite in polarity to a voltage VDD fed to the drain of the dual gate FET 40, and a control voltage V12 of the same polarity as the voltage VDD fed to the drain of the dual gate FET 40 is fed to the base of the TR 61. A control voltage V121 changing over a positive and negative voltage range is extracted from a connection midpoint between the 1st and 2nd elements 63, 64 corresponding to the control voltage V12. The extracted control voltage V121 is fed to the gate of the dual gate FET 40 to control the gain. |
