GB859320A - Improvements in or relating to pulse generating circuits - Google Patents

Abstract

859,320. Transistor pulse circuits. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Sept. 6, 1957 [June 22, 1956], No. 19485/56. Class 40(6) In a transistor pulse generator of the kind in which the output pulse duration is determined by a time-constant circuit comprising a resistor connecting the emitter of a transistor to its supply terminal and a capacitor connected to the emitter, the second terminal of the capacitor is connected to a second transistor, to determine the initial potential at the second terminal of the capacitor. In the quiescent state of the circuit shown transistor TA is conducting, TB non- conducting and TC conducting, the potential V2 at the collector of TC determining the potential at the left hand terminal of a timing capacitor C. An input pulse applied to the base of transistor TA will diminish in collector current and by regenerative action through TB transistor TA will be rapidly cut off and TB will become fully conducting so that the potential at the left hand terminal of the capacitor will fall to the collector potential of TB (-12v). The capacitor will now charge at a rate determined by resistor Rl until transistor TA commences to conduct, whereupon by regenerative action the circuit returns to its initial condition. The pulse amplitude and duration may be varied by varying the potentials of the collectors of transistors TB and TC and a constant current transistor may be connected in series with the emitter of transistor TA. The transistor TA may be held on a linear part of its characteristic during the quiescent condition by choice of resistor R2 or by means of a diode D.