GB930595A - Transistor oscillators - Google Patents

Abstract

930,595. Transistor oscillator circuits. JOSEPH LUCAS (INDUSTRIES) Ltd. March 21, 1962 [April 25, 1961], No. 14869/61. Class 40 (6). An oscillator comprises a capacitor 5 connected across a source of supply, a transistor 6 having its collector electrode connected to a first terminal of the source, its emitter electrode connected through a first relay core 7 to the second terminal of the source and its base electrode connected to the first and second terminals of the source through a resistor 8 and a capacitor 9 respectively, and a second relay coil 12 connected in series with a normally open relay contact 13 across the terminals of the source, both relay coils acting when energized to close the contact 13 and the closure of said contact serving to initiate discharge of capacitor 9. The circuit may supply pulses for lighting a neon lamp connected across the secondary winding 15 of a transformer 11. A diode 16 may be connected as shown between the junction of winding 12 and contact 13 and the base of transistor 6; preferably, however, source 4 has a high resistance in which case the diode connection is omitted. With a high-resistance source 4 capacitor 9 charges until sufficient current flows through relay winding 7 to cause contact 13 to close. This completes the circuit through winding 12, thus making the closing of contact 13 more positive. However, since windings 10 and 12 are of low resistance, the potential at the collector of transistor 6 falls and capacitor 9 discharges through the base-collector diode until insufficient current flows through winding 7 to maintain contact 13 closed, whereupon the cycle repeats. If, however, source 4 has a low resistance, the potential at the collector of transistor 6 will not fall sufficiently when contact 13 closes to discharge capacitor 9. In this case diode 16 is provided through which capacitor 9 discharges when contact 13 closes.