| 摘要 |
PROBLEM TO BE SOLVED: To provide a simple circuit configuration in which stable oscillation signals with an appropriate amplitude level can be produced. SOLUTION: The polarity of the voltage between a first input terminal 8 and a second input terminal 10 in a first differential amplifier circuit 4 is reversed every half period of the transmission signal Vout. Therefore, in a transistor Q1 and a transistor Q2, the base and the emitter are alternately reverse- biased, and the voltages in the bases of the transistors Q1, Q2 appear alternately in the emitters of the transistors Q1, Q2, so the lip component of the emitter voltage Va becomes similar to the fully-rectified waveform of the transmission signal Vout. The current control circuit 6 generates the control voltage 20 by smoothing the emitter voltage Va and applies it to the base of the transistor Q4. As a result, the larger amplitude level of the transmission signal Vout reduces the idling current I0 as the amplification degree decreases. Conversely, the smaller amplitude level of the transmission signal Vout raises the idling current I0 as the amplification degree increases.
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