Pulse generator

1,149,135. Transistor pulse generators. STARKSTROM-ANLAGENBAU KARL-MARX. STADT VEB. 26 Sept., 1967, No. 43670/67. Heading H3T. In a pulse generator having a sawtooth Schmitt trigger generator I with a variable time constant R.C. integrating network R1/I, C1/I feeding via an impedance transformer II a further Schmitt trigger III, the Schmitt trigger III has its common emitter resistor replaced by a transistor T8 which has its collector current adjustable to a constant value by means of a voltage divider III.1 and the base of the output transistor T7 of the Schmitt trigger III is connected to a potentiometer III.2 for adjustment of the pulse duration to space ratio. When the supply E.M.F. is connected the potential at B rises negatively due to C1/I charging and when a certain value is reached the Schmitt trigger circuit I.1 changes state, T2 turns ON and T3 turns OFF. The negative going output at C is coupled via Zener diode D1 to the base of T4 which together with T5 turn ON so that the capacitor C1/I is discharged via T5. The trigger circuit I.1 then assumes its initial state and the above operation is repeated. When the sawtooth voltage produced at B reaches a certain value the Schmitt trigger III changes state T6 turns ON and T7 turns OFF. T6 remains on until the sawtooth voltage falls in value when the trigger circuit III returns to its initial state. This process is repeated to produce a pulse output at D of constant amplitude, the duration to space ratio being set by the adjustment of III.2. Zener diode D2 maintains the potential at G constant.