| 摘要 |
PURPOSE:To control the gain at high frequencies stably, by connecting both emitter electrodes of a transistor (TR) constituting a differential amplifying circuit with a capacitor. CONSTITUTION:The gain of a differential amplifying circuit shows f<1/2> (where; f is frequency) by a capacitor 37 and emitter resistors 35, 36 provided between both emitters of TRs 31, 32 constituting a differential amplifying circuit. Both emitter electrodes of the TRs 31, 32 are connected to the collector of a TR38 being a current source via the resistors 35, 36. The TRs 38, 39 are connected differentially. The emitter AC resistor of the TRs 35, 36 is changed by controlling the base potential of the TR39. As a result, since the gain is controlled, the characteristics of f<1/2> and the loss of transmission line are suitably compensated. |
