GB1393767A - Oscillator circuits - Google Patents

Abstract

1393767 Keying oscillators; magnetic storage arrangements WESTERN ELECTRIC CO Inc 13 July 1972 [19 July 1971] 32779/72 Headings H3B and H3R An oscillator circuit includes a tuned circuit having a capacitor and at least one inductor, means for precharging the capacitor, switch means responsive to an energizing signal for completing a loop including the tuned circuit to initiate an oscillatory current therein, means for maintaining the oscillatory current at a predetermined value, and means connected across the switch means for terminating the oscillatory current at the end of an oscillation cycle upon removal of the energizing signal during a predetermined portion of the cycle. In a tuned circuit comprising capacitor 1, Fig. 1, main inductor 19 and auxiliary inductor 9, the capacitor 1 is held charged, in the static condition, by means of a current source comprising resistor 8. Upon an energizing signal e 1 being applied to its base, transistor 4 becomes conductive and closes the tuned circuit, which is then maintained in an oscillatory condition by means of amplifier 5, which derives an input from point 26 over 90 degrees phase-shifting circuit 11, and is biased from source E2 to provide class C operation. When the energizing signal e 1 is terminated oscillations cease; diode 3 connected in the reverse direction to the base-emitter junction of transistor 4 ensures that the oscillations terminate at the point in the cycle at which capacitor 1 is fully charged. Magnetic domain propagation circuit.-For use in such an arrangement, two of the abovedescribed circuits may be combined so as to provide a rotating magnetic field, the inductors 2, 2<SP>1</SP>, Fig. 2, of the two circuits 20, 30 being arranged mutually, perpendicular. The base of the transistor 4 is coupled directly to the control circuit 17, while the base of the transistor 4<SP>1</SP> is coupled thereto over a delay network 16. In addition, the device for the amplifier 5<SP>1</SP> is derived from the point 26 in the circuit 20, without interposition of a 90 degree phase-shifter. The control circuit 17 comprises a bi-stable circuit 27, the initiating control signal e 1 being applied to its "set" input S and also to AND gate 29 and OR gate 28. Switching off is determined by an input to the "reset" input R which is derived from AND gate 24, the two inputs to which are derived from input e 1 and a signal derived over diode 21 from the tuned circuit 1, 2: the latter ensures that switching off is performed in the correct part of the oscillation cycle. The Specification also describes a modification of this arrangement (Fig. 3, not shown) in which switches are provided whereby the direction of rotation of the magnetic field can be reversed.