GB684626A - Improvements in or relating to electric amplifier arrangements of the kind which includes a magnetic amplifier - Google Patents

Abstract

684,626. Deaf aids. GENERAL ELECTRIC CO., Ltd., and HAMER, E. G. March 21, 1951 [March 28, 1950], No. 7768/50. Class 40 (iv). [Also in Group XL (c)] An electric amplifier arrangement comprises a magnetic amplifier which is supplied with alternating current from a crystal contact oscillator, the only necessary source of electric supply being direct current. The invention is suitable for deaf-aid apparatus. In Fig. 1, the input signal, which may be D.C. or A.C., is applied to control winding 8 on saturable core transformer 3. Oscillations at a higher frequency are applied to primary winding 5 on the transformer, and the output, consisting of a modulated wave, is taken from winding 6, rectified, and applied to load 18 which may be a telephone receiver. The oscillations are produced by a crystal triode oscillator, the tuned circuit 5, 25 being connected effectively between the base electrode and both the emitter and collector electrodes. Bias for the electrodes is supplied by battery 27, which is the only source of energy for the amplifier. Oscillations are produced due to the current-gain characteristic of the transistor. In an alternative arrangement the emitter is coupled to the collector circuit by a separate coil on the same transformer leg. The audio frequency response of the device may be modified by varying condenser 19 across the load 18. An additional winding may be provided to produce the polarizing magnetic flux for the transformer if the direct current through coil 5 is insufficient, and a further modification provides for the use of a transformer of toroidal construction.