| 摘要 |
An amplifier for amplifying high frequency signal comprises cascade-connected an input npn transistor and an output npn transistor. A bias circuit is provided to control a base current Ib of the input transistor in order to make a DC component of a collector current Ic of the cascade-connected npn transistors to be constant. A shunt transistor is further connected between a base electrode of the input npn transistor and one terminal of a power source. It is so constructed that the base current of the input npn transistor flows through a resistor connected between a base electrode and an emitter electrode of the shunt transistor. By lowering a base voltage of the output npn transistor in response to a gain control signal, the collector current Ic is reduced, and a gain of the amplifier is reduced, and simultaneously the shunt transistor is made in shunting operation. <IMAGE> |
