| 摘要 |
PURPOSE:To eliminate a decrease and variance in detection sensitivity and to improve the stability of an oscillation frequency and temperature characteristics by controlling the phase characteristics of the amplifying element of an oscillator through a variable capacitor and varying the oscillation frequency. CONSTITUTION:The series circuit of an inductor L1 and capacitors C1 and C2 constitutes an LC parallel resonance circuit. The LC parallel resonance circuit is connected to the collector of a transistor (TR) Q for amplification and a feedback path F for oscillation is provided from the connection point between the capacitors C1 and C2 to the emitter of the TRQ. Further, resistances R1-R3 are applied with the bias of the TRQ and a coupling capacitor C4 cuts the DC component in the output of an oscillator. A capacitor C3 for adjustment is provided between the collector and base of the TRQ. Then, the TRQ varies in phase shift amount with the value of a capacitor C3, so the oscillation frequency is adjusted. |
