Patent GB-1025331-A (GB)
Title: Improvements in or relating to pulse generators
Inventor: KANDIAH KIRTHIRKAMATHAMBY
IPC: H03K5/156
Filed: 1961-04-07
Abstract: 1,025,331. Transistor circuits. UNITED KINGDOM ATOMIC ENERGY AUTHORITY, July 6, 1962 [April 7, 1961], No. 12713/61. Heading H3T. [Also in Division G4] Apparatus for generating a train of pulses the amplitudes of which are modulated by a triangular waveform comprises a Miller integrator supplied with a voltage the polarity of which is reversed by an electronic switch controlled by the output of the integrator so as to define the positive and negative limits of the triangular waveform. The waveform so generated is used to control a pulse amplitude modulator the output of which is employed in the determination of channel widths of a pulse amplitude analyser. Self-oscillating triangular wave generator.- Fig. 2 shows a Miller integrator comprising an electrometer valve V1 and transistors J1, J2, J3 with feedback provided via a capacitor C1. J2, J3 form a long-tailed pair having a constant current collector load formed by the NPN transistor J4. The voltage to be integrated is successively changed from + 10 v. to - 10 v. under control of a bi-stable circuit comprising transistors J10, J11. Adjustable D.C. voltages developed by passing constant current controlled by J6, J7, through variable resistors VR1, VR2, respectively govern the lower and upper limits of the triangular waveform generated. These voltages are fed in series with the output of the integrator via emitter followers J5, J8 to the bi-stable switching circuit J10, J11. The conductive states of transistors J10, J11 are reversed whenever the integrated output reaches its upper or lower limit, reversing the conductive state of the complementary transistors J12, J13. These transistors are coupled together via a pair of Zener diodes Z1, Z2 hence each time the limit is reached, the output from the emitters of J12, J13 changes from +10 v. to -10 v. or vice versa. Switch S1 is opened when it is desired to stop oscillation. The integration then continues until an output of approximately one volt greater than the negative limit is reached, when transistor J14 and diode M1 become conductive, closing a negative feedback path around the integrator and inhibiting its action. A switch (not shown) is provided to adjust the duration of each triangular wave between the limits of 10 seconds and 200 minutes. Blank switch positions are provided so that the sweep can be stopped at any voltage. Transistor chopping or pulse modulating circuits.-The triangular waveform at the collector of transistor J2 is fed via R21 to a circuit comprising transistors J15, J16. Unmodulated pulses from an oscillator (not shown) are fed via current transformers T1, T2 and diodes MR4, MR5 to transistors J15, J16 which become conductive during each pulse, clamping the voltage at the junction of resistors R21, R26 to earth. Diodes MR4, MR5 become non- conductive at the end of each pulse, hence stored charges are dissipated slowly, thus eliminating spurious steps in the collector circuit. The final output available via capacitor C4 thus consists of a train of pulses amplitude modulated by positive and negative triangular waveforms. The transistor modulator circuit may be replaced by a mercurycontact relay.