GB996980A - Tunnel diode logic circuits - Google Patents

Abstract

996,980. Tunnel diode logic circuit. RADIO CORPORATION OF AMERICA. Sept. 4, 1961 [Sept. 19, 1960], No. 31767/61. Heading H3T. An inverter, minority gate or majority gate comprises a balanced power supply and signal input and output terminals connected to a pair of series connected tunnel diodes. Referring to Fig. 1, two GaAs tunnel diodes 50, 52 are connected in series between a source of positive pulses 58, and a source of negative pulses 60. The amplitude of the pulses and the values of the resistors 54, 62, 56, 66 may be arranged either so that the circuit has two or three stable states. Inputs 74, 76, 78 for example, are connected to the anode of diode 50, and to the cathode of diode 52. Assuming a positive potential is applied to, say, input 74 diode 50 will be forward biased, and diode 52 reverse biased, and application of the pulses from sources 58, 60 will cause diode 50 to switch to its high state, and diode 52 to switch to its low state, resulting in a negative potential at the output terminal 94. Conversely a negative input will produce a positive output. Application of three inputs gives a minority logic circuit, i.e. if two inputs are positive and one negative the total input is positive resulting in a negative output. A mixed minoritymajority circuit may be produced by adding inputs 89, 91 connected to the junction of the two diodes. In a second embodiment, Fig. 3, the input and output terminals are interchanged and each series arrangement of tunnel diode and load resistor is shunted by a diode 110 or 112 which may be Ge backward diodes or low peak tunnel diodes, the arrangement being so that when tunnel diode 102 is conducting heavily diode 104 is shunted by diode 124, and when tunnel diode 104 is conducting heavily diode 102 is shunted by diode 120. In a modification of the circuit of Fig. 1, Fig. 5 (not shown) the inputs are connected across the two tunnel diodes by individual resistance networks, and in a modification of the circuit of Fig. 3, Fig. 6 (not shown) a pair of Ge backward diodes or low peak tunnel diodes are connected in reverse parallel between the junction of the two tunnel diodes 102, 104 and earth in place of the diodes 110, 112. If the circuit is arranged to be bi-stable, it may be biased so that in the absence of an input signal of either polarity, there is no ambiguity of the state it takes up.