| 摘要 |
912,143. Transistor pulse generating circuits. DIETZ CO., R. E. Jan. 28, 1960 [July 15, 1959], No. 3133/60. Class 40 (6). A circuit for energizing a flashing lamp 26 comprises a free-running pulse generator constituted by two reciprocally-coupled transistors 14, 16 of opposite conductivity types and a further power transistor 10 controlled by the pulses from the generator 14, 16 to supply pulses of current to the lamp 26. The pulse generator constituted by transistors 14, 16 is substantially the same as that described in Specification 884,301. Considering a cycle of operation starting from the condition in which the transistors are cut off and capacitor 56 is substantially discharged, the capacitor charges negatively until transistor 16 conducts, the current flowing through the transistor causing transistor 14 to conduct also, thereby sending the base of transistor 16 further positive and increasing conduction in the transistors due to the voltage drop produced across load resistor 42. The capacitor 56 discharges until its potential falls so low that conduction in one or other of transistors 14, 16 cannot be maintained and the transistors then switch off by regenerative action. The load resistor 42 may be constituted by a small lamp if desired. A parallel combination of inductor 22 and resistor 24 is arranged in series with the lamp 26; this ensures a large effective load before the lamp 26 warms up so that transistor 10 is driven into saturation immediately on being switched on. The capacitor 12, which does not appear in the circuit shown in Specification 884,301, maintains the potential of the base of transistor 16 steadier than would otherwise be the case and so slows the discharge of capacitor 56 and increases the duration of the " on " period of the circuit. Reference has been directed by the Comptroller to Specification 801,453. |
