| 摘要 |
844,411. Transistor oscillators. FIELDEN ELECTRONICS Ltd. Dec. 1, 1958 [Dec. 5, 1957], No. 37864/57. Class 40(6). [Also in Group XXXVI] A transistor oscillator comprises a tapped induction 2, the two parts of which are tightly coupled, connected in parallel with two series capacitors 3, 4, and a transistor 1 whose emitter-base path is connected in series with an inductor 15 between the junction of the capacitors 3, 4 and the tapping point 9 on the inductor 2. The ratio of the capacitors 3, 4 is chosen in relation to the tapping point 9 to provide sufficient positive feedback at the base of transistor I to maintain oscillations. The inductor 15 is chosen to series-resonate with the capacitance provided by the capacitors 3, 4 in the feedback path from the emitter of the transistor and in which they are effectively in parallel. Thus when the tapping point is at the centre of the inductor 2, the value of inductor 15 should theoretically be onequarter that of inductor 2, though in practice a slightly greater value is found necessary due to stray capacitances. The inductor 15 also serves to isolate the voltage-sensitive capacitance at the base and collector electrodes from the capacitor 4. It is stated that the circuit may be modified so that the base electrode is connected through the inductor 15 to the tapping point 9, while the emitter electrode is connected for oscillatory currents to the junction point of the capacitors 3 and 4; alternatively the transistor may be connected so that its base electrode and its collector electrode is common to both its input and output circuits. In Fig. 2 (not shown) a probe is connected to the junction of capacitors 3 and 4 and an output circuit is provided to measure the amplitude of oscillation in the circuit, this indicating the proximity of the probe 17 from a conducting object. |
