Cascode amplifier with an improved biasing arrangement

摘要

A cascode amplifier comprises a grounded-emitter drive transistor which has a collector supplied with a bias current from a bias current source and operates in response to an input signal and a grounded-base (or grounded-gate) output transistor which has a collector supplied with a bias current from a constant voltage source, wherein the collector of the drive transistor is connected to the emitter (or source) of the output transistor. A constant current circuit is connected to the junction between the collector of the drive transistor and the emitter (or source) of the output transistor for supplying a part of the bias current applied to the drive transistor to thereby decrease the bias current of the output transistor while causing the drive transistor to be operated in the linear region. The cascode amplifier is thus imparted with a broad band frequency characteristic.