| 摘要 |
PROBLEM TO BE SOLVED: To obtain superior noise characteristics, low power consumption, excellent yield, and low distortion characteristics by constituting a multistage connection amplifier which is equipped with amplifiers composed of homogeneous junction type bipolar transistors (BJT) and amplifiers composed of heterogeneous junction type bipolar transistors (HBT) and has an amplifier composed of HBT as its final stage. SOLUTION: A high-frequency signal is inputted to an input terminal 1 and amplified by a BJT amplifier 3 and further by an HBT amplifier 4, and then outputted to an output terminal 2. The BJT amplifier 3 has low noise and high gain, but has large distortion. The HBT amplifier 4, on the other hand, has low noise and high gain and further small distortion. A BJT amplifier 3 is used as the initial-stage amplifier which is dominant to noise characteristics, so low noise characteristics are obtained; and an HBT amplifier 4 is used as the final-stage amplifier which is dominant to distortion characteristics, so small distortion characteristics are obtained.
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