Patent GB-1233722-A (GB)
IPC: H03K3/287
Filed: 1968-05-10
Abstract: 1,233,722. Transistor switching circuits. RCA CORPORATION. 10 May, 1968 [5 Sept., 1967], No. 22268/68. Heading H3T. [Also in Division G4] In an integrated circuit including emitter coupled transistors 22, 23 and resistors 30, 32, 33 the collector of a further transistor 25 is connected to the resistors 32, 33 and uncommitted connection points are provided to the collectors at 13, 14, the bases at 5, 10 and 18 and the emitter at 19. These points may be connected in different manners to provide gates, adders, shift registers, counters, bi-stable and other switching arrangements. The circuit shown in Fig. 1 is formed as an integrated unit arid two or four such circuits can be formed on a single chip. Fig. 2 shows a gate circuit capable of OR, NOR or AND, NAND functions and providing from 600 mV input signals 600 mV outputs at Q, Q. Either transistor 22 or 23 is on depending on the inputs applied at A, B and C as compared with Vref provided by resistor chain 34, 35, 36. Transistors 25 and 26 are connected as diodes and provide temperature compensation and power supply tracking. Input voltage level shift is provided by the base-emitter junctions of transistors 27, 21, 24. The diode connected transistor 26 may be shared with neighbour circuits on the same chip. Also transistor 26 could be a PNP type having its collector and base electrodes connected to Vps and emitter to point 48. The circuit of Fig. 1 may be connected as a bi-stable circuit, Fig. 4, having reset inputs 12 and 3. The set input may be obtained from the Qp output transistor 24 of the gate of Fig. 3 and is applied to 18. Increasing fan in claimed in Specification 1,233,723.-The point 3, Fig. 2, may be used to expand the input using expander units (transistors 21 and 27) borrowed from other similar cells or circuits. Also the point 3 may be driven from emitter follower outputs of other gates such as Qp of Fig. 3 which provides an OR function, and has transistor 24 providing this output. The transistor 24 can provide a dual function by forming the output transistor of Fig. 3 gate and as an input expander for a gate or bi-stable circuit (Figs. 3 and 4). Fan in of the gate or bi-stable circuits may be increased by taking components from circuits where less fan in is required. In a further gate circuit, Fig. 5, in the form of a receiver, driver gate inputs A, B, C between -800 mV and -1400 mV are applied to 1, 2 and 5 and outputs Q, Q, are between 0 and -600 mV whereas output Qp is one base emitter voltage below this between -800 mV and -1400 mV. The inputs therefore may be from the Qp output of a similar gate circuit or gate of Fig. 3. In a modified form of Fig. 5 a mixer receiver gate (Fig. 6, not shown) point 4 is joined to 5 and 6 and connection 51 is removed so that the C input is connected to 7. This differs from the Fig. 5 gate in that the required signal input C is between 0 and 600 mV which may be obtained from the Q, Q outputs of any of the previously described gates. The gates of Figs. 3 and 5 may be modified by shorting out part of the emitter resistor 30 between terminals 8 and 17 (Figs. 7 and 8, not shown). This provides larger output voltage drops across collector resistors 32, 33 such as 800 mV. In an alternative modification of Fig. 5 (Fig. 9, not shown), part of the resistor 36 is shorted between terminals 9 and 18 so as to shift the reference voltage Vref and provide a threshold for a 800 mV input signal swing A, B or C. Output signals from Q, Q, and Qp still have a O-600 mV swing. In a system using these gates (Fig. 10, not shown) claimed in Specification 1,233,724, an external circuit (71) providing an output of 800 mV feeds an integrated circuit chip (70) including gate (74), e.g. of Fig. 9, in cascade with a 600 mV array circuit (73) and a circuit (75) which converts the 600 mV signal to 800 mV for feeding a further external circuit (72).