| 摘要 |
PURPOSE:To obtain a contactless switch free of variation in sensitivity by eliminating influences of floating capacity and a DC bias component, by inserting a capacitor in parallel to the base and emitter of a transistor (TR) for oscillation. CONSTITUTION:The bases of TRs 11 and 12 are connected mutually and the resonating circuit consisting of a capacitor 13 and a detection coil 14 is connected to the emitter of the TR11. Further, a capacitor 18 is connected in parallel to the base and emitter of the TR11, and the emitter output of the TR12 is fed back to the said resonating circuit through a resistance 16. The capacitor 18 performs the AC by-passing of the DC bias component of the base-emitter forward voltage of the TR11, so influences of the floating capacity of the circuit due to IC-implementation and a DC bias component are excluded. |
