GB996171A - Improvements relating to electrical apparatus - Google Patents

Abstract

996,171. Transistor multistable state and logic circuits. ELECTRIC & MUSICAL INDUSTRIES Ltd. Sept. 7, 1961 [Sept. 17, 1960; Feb. 22, 1961], Nos. 32042/60 and 6415/61. Heading H3T. [Also in Divisions G4 and H1] Basic logic circuits each comprising, for example, a transistor 3, resistors 4, 7 and capacitors 2, 9 may be coupled together to perform various functions. In a shift register, Fig. 1, pulses applied at input 1 are differentiated and fed to the base of a first transistor 3. Antiphase shift pulses A, B are applied to alternative transistors in the register, and upon shift pulse A going negative coincident with the negative-going pulse derived from differentiating the input, transistor 3 conducts passing a pulse on to transistor 11. This pulse is in turn differentiated and causes transistor 11 to conduct when shift pulse B goes negative. An inhibit gate may be formed by coupling the output of transistor A2, Fig. 4, to the input of transistor A4 and feeding a second input into A3. Information pulses applied to A3 are fed through A4 as described previously except when an inhibit signal is applied to input 20. Under this condition a positive pulse is produced at the input to A4 to cancel the negative pulse from A3. A number of inhibit gates may be combined with single stages to form a full adder, Fig. 6 (see Division G4). In this Figure inhibit gates 101, 104 and single stages 102, 103 form an " exclusive OR " gate. In modifications of the circuit the shift pulses may be fed through diodes, and the capacitive couplings may be replaced by transformer couplings. In a further modification an A.C. polarizing supply may be used for the transistors, in which case the shift pulses may if desired be replaced by a fixed bias.