LOW NOISE AMPLIFIER AND COMMUNICATION PORTABLE TERMINAL USING THE AMPLIFIER

摘要

PROBLEM TO BE SOLVED: To reduce parasitic capacity which additionally occurs and to suppress the deterioration of the ability of a transistor by eliminating a potential difference between the emitter terminal and the sub-terminal of the transistor. SOLUTION: A received high frequency signal inputted from an input terminal 1 is amplified and it is outputted from an output terminal 2. An input matching circuit 3 and an output matching circuit 4 are lumped constant circuits constituted of first capacity 3a, inductance 3b and second capacity 3c and they convert impedance into desired one. The emitter terminal 8b and the sub-terminal 8c of the transistor 8 are grounded and the potential difference between the terminals 8b and 8c is eliminated. Parasitic capacity which additionally occurs in the transistor is reduced and the deterioration of the ability of the transistor is suppressed. Since the deterioration of the ability of the transistor is suppressed, emitter resistance (feedback resistance) is eliminated and therefore current may become unstable. It is desirable to add an active feedback bias circuit at that time.