| 摘要 |
PURPOSE:To stabilize oscillation amplitude by connecting the base of a transistor (TR) whose collector is connected to a power source and the collector of a TR for a level shifting circuit to the base of an emitter follower TR. CONSTITUTION:The output current of the Tr1 connected into an emitter follower is fed back to the parallel resonance circuit consisting of a detection coil L and a capacitor C through the current mirror circuit consisting of Trs 2 and 3. The base of the Tr7 whose collector is connected to the power source and the collector of the Tr6 of the level shifting circuit consisting of resistances R1 and R2 and the Tr6 are connected to the base of the Tr1. The level shifting circuit is supplied with a constant current IB from the current mirror circuit consisting of Trs 4 and 5. Currents flowing through the resistances R1 and R2 are supplied from the power source side through the Tr7, so variation in bias voltage due to the temperature drift of the Tr1, etc., is prevented and the oscillation amplitude is stabilized to decides on the approach of an approaching body accurately. |
