GB987948A - Improvements in or relating to amplifying circuits for electronic digital computers - Google Patents

Abstract

987,948. Transistor amplifying and pulse generating circuits. GENERAL PRECISION Inc. Aug. 27, 1963, No. 33811/63. Heading H3T. An arrangement for amplifying clock signals from a movable magnetic memory and generating sharp clock pulses in response thereto comprises a pre-amplifier stage feeding into a series resonant circuit which provides discrimination against random noise. This is coupled to a squaring circuit feeding a differentiating circuit, thereby generating trigger pulses which trigger a monostable flip-flop to produce a series of output pulses short in duration compared with a corresponding half-cycle of sine wave clock signal input. Sine wave signals from read head winding 18 are applied in push-pull to the bases of a pair of PNP transistors 24, 26, via series resistors 20, 22. The transistors 24, 26 form an emitter-coupled pair, individual emitter resistors 44, 48 being provided together with a coupling capacitor 28. The collector circuits comprise resistors 34, 36, the collectors being direct coupled to the bases of NPN transistors 30, 32 which form a second emitter coupled pair having individual emitter resistors 38, 40 and a coupling capacitor 50. The collector circuits comprise resistors 42, 46, negative feed-back being provided between these collectors and the bases of the opposite first stage transistors by means of resistors 52, 54. The output is taken from the collector of transistor 30 and is applied via series resonant circuit 102, 104, which discriminates against random noise, to the base of a transistor 106 which acts as a squarer, being driven between cut-off and saturation. Diode 108 is provided across the base-emitter path, being conductive when transistor 106 is driven non-conductive and maintaining the same load on the preceding circuit as is present when 106 is driven conductive. The square wave output from the collector of transistor 106 is differentiated by a circuit comprising capacitor 112 and resistor 114, the positive-going components of the sharp pulses so produced being passed by a diode 116 to trigger a monostable flip-flop 13. The pulses are applied to the base of a transistor 118 the collector of which is coupled to the output terminal C p and base of transistor 134 over an emitter-follower 126 and RC network 128, 130, the collector of transistor 134 being back-coupled to the base of transistor 118 over capacitor 142. A diode 124 shunts the baseemitter path of transistor 126. Transistor 118 is normally biased conductive via resistors 120, 122, transistor 126 is slightly conductive and transistor 134 biased non-conductive via resistors 136, 128. Each positive pulse makes transistor 118 non-conductive, rendering transistor 126 fully conductive whereby the base of transistor 134 goes negative and it becomes conductive. Capacitor 142 holds transistor 118 non-conductive until it has charged sufficiently, whereupon the flip-flop restores to its original state.