Patent GB-999047-A (GB)
Title: Memory circuits employing negative resistance elements
IPC: H03K3/315
Filed: 1961-08-28
Abstract: 999,047. Semi-conductor circuits. RADIO CORPORATION OF AMERICA. Aug. 28, 1961 [Sept. 12, 1960; Jan. 12,1961], No. 30995/61. HeadingH3T. [Also in Division G4] A digital data storage circuit comprises a tunnel diode and another form of diode connected so that one acts as the load on the other, the state of the circuit being determined by feeding a pulse through one diode to the other. Circuits are described in detail by using the characteristics of one diode as a load line on the characteristics of the other. Fig. 1 shows a germanium tunnel diode 10 and a gallium arsenide tunnel rectifier 14 fed with constant current via resistor 18. The characteristics of the tunnel diode are shown at 34 in Fig. 3 and those of the tunnel rectifier (also known as a backward diode) by the heavy line 36-42. The circuit has two stable states corresponding to the two points where the positive resistance parts of the tunnel diode characteristic 34 cut the load line 44, representing resistor 18. A binary ONE is written into the store by applying a positive signal to line 24 and a negative signal to line 20. This sets the tunnel diode 10 into its low voltage stable state. The store may be read without destroying the information by feeding a negative pulse on line 24. If the store is in its binary ONE state, a pulse will be fed to the amplifier 28. The store may be simultaneously read and reset to ZERO by feeding a larger negative pulse on line 24. Fig. 6 (not shown) relates to a similar circuit in which the tunnel diode is biased by a series battery and the read and write pulse sources are connected in series with the respective diode. Fig. 8 (not shown), relates to a further similar circuit in which the polarity of the tunnel diode is reversed. Fig. 10 shows a circuit in which the constant current source is replaced by a series supply such as battery 88<SP>1</SP>. A resistor 108 is connected across the tunnel rectifier 14<SP>1</SP> so that the zero current region of its characteristic is converted to a positive resistance region. Storage, circuits using a tunnel diode and a conventional diode.-Fig. 12 shows a circuit comprising a tunnel diode 120 and a conventional diode 134. A binary ONE is written into the circuit by simultaneous application of positive pulses to the X and Y lines. This sets the tunnel diode 120 into its high voltage stable state. The circuit is read by emitting a positive or negative pulse from source 130. If the circuit is in its ONE state a pulse will be passed by transformer 138 and diode 144 to output terminals 142. The circuit may be simultaneously read and reset by emitting a larger amplitude negative pulse from source 130. Fig. 13 (not shown) relates to a similar circuit in which the positions of the tunnel and conventional diodes are reversed. Matrix data stores.-Fig. 4 shows a memory plane in which each element comprises a tunnel diode 10-4 and a tunnel rectifier 14-4. Data is written into the circuit by simultaneous application of pulses applied to selected bit lines 20o- 20d and word lines 24a-24d. The word stored in all the elements connected to line 24a may be read by applying a negative pulse to that line. A pulse will then be fed to the appropriate sense amplifier 28-1 corresponding to the element in the ONE state. Fig. 16 (not shown) relates to a memory plane using tunnel diodes and positive resistance diodes.