| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a sufficient amplification degree with respect to each frequency by selecting a capacitor in a parallel resonance circuit and a bypass capacitor of an amplifier transistor(TR) so as to allow each capacitance to provide a sufficiently small reactance with respect to each frequency. SOLUTION: A parallel resonance circuit 36 is connected to an output terminal of an amplifier TR 7 and a bypass capacitor 34 is connected between a ground terminal and a reference potential point. The parallel resonance circuit 36 includes two capacitors 32, 33 and a switch means 35 is provided between the connecting point and the reference potential point. The capacitance of the capacitor of the capacitors toward the reference potential point is selected to provide a sufficiently small reactance at a low frequency, the 1st frequency, and the capacitance of the bypass capacitor 34 is selected to provide a sufficiently small reactance at a high frequency, the 2nd frequency. Thus, the parallel resonance circuit connecting to the amplifier TR or the bypass capacitor is selected corresponding to the frequency and a sufficient amplification factor is obtained for the respective frequencies.</p> |
