GB765472A - Improvements in and relating to blocking oscillator circuits - Google Patents

Abstract

765,472. Pulse generator circuits. LEVELL, D. A. Jan. 7, 1955 [Jan. 21, 1954], No. 1834/54. Class 40(6) The amplitude of a pulse generated by a blocking oscillator circuit is maintained substantially constant by applying to an electrode of the blocking oscillator tube when the predetermined amplitude is attained a voltage which maintains the current in the tube substantially constant. The Figure shows a blocking oscillator circuit of which the pulses generated have their duration maintained constant by delay line 18. The blocking oscillator tube 12 has trigger impulses applied to its control grid from terminal 10 via diode 11 the negative swing of the grid being limited by diode 20. Tube 25 is normally cut off by the negative voltage applied to its control grid from terminal 31. When a positive trigger impulse is applied at input 10 the blocking oscillator tube 12 is cut off, the anode voltage goes negative and due to the action of transformer 13 a positive pulse is generated at terminal 24 and is ultimately terminated by reflection of a negative pulse to the control grid of tube 12 from the end of delay line 18. If the positive pulse at output 24 tends to increase in amplitude a positive voltage is applied via frequency compensated attenuated circuits 26, 28, 27, 29 to the control grid of pentode 25, the resulting negative voltage at its anode being applied to the screen grid of blocking oscillator tube 12 to maintain the current in this tube constant. Thus any tendency for the pulse at output 24 to change in amplitude is compensated by the feed-back circuit comprising pentode 25. If it is required to change the amplitude of the output pulse at 24 whilst maintaining a substantially constant duration this may be effected by adjusting the setting of potentiometer 30.