GB678317A - Improvements in sine wave semi-conductor oscillators - Google Patents

Abstract

678,317. Semi-conductor circuits. RADIO CORPORATION OF AMERICA. Jan. 30, 1950 [Jan. 28, 1949], No. 2367/50. Classes 40 (v) and 40 (vi). An oscillator comprises a transistor, the electrodes being biased so as to provide a negative resistance between the base electrode and a point of reference potential, and a resonant circuit being connected between the base electrode and the said point. Fig. 2 shows a transistor comprising a block of semi-conducting material 1, base electrode 4, emitter electrode 2 and collector electrode 3. A parallel resonant circuit is connected between the base electrode 4 and ground, and with suitable biasing potentials applied to the emitter and collector electrodes, a negative resistance characteristic exists between the base electrode and earth, so that oscillations are produced. The output may be taken from the resonant circuit by an inductive coupling 17. A method of measuring the negative resistance between base electrode and earth is described, this characteristic being a function of the emitter bias. Alternative arrangements provide for the base electrode to be connected to a tapping on the inductance of the resonant circuit, or for the output to be taken from the collector by resistance capacity coupling. Fig. 7 shows a modification in which phase shift networks 27, 32 and 22, 33 are included in the collector and emitter circuits respectively, which allows oscillations to be produced at higher frequencies. Alternatively, a seriesresonant circuit may be connected between the collector and earth or between the emitter and earth to improve operation at higher frequencies, and the output may be taken from a coupling with the series resonant circuit. In a further arrangement, oscillations at a harmonic frequency may be produced by providing a parallel resonant circuit tuned to a harmonic frequency, in the collector circuit. Keying of the oscillator may be provided by applying signal pulses, which may be width or time modulated, to either the emitter or the base electrode, the biasing arrangement being such that these electrodes are biased in a non- conducting direction except when pulse signals are applied, so that oscillations are produced only during the occurrence of each pulse.