Patent GB-1121526-A (GB)
Title: Memory storage unit employing insulated gate field effect transistors
IPC: G11C11/413
Filed: 1965-08-06
Abstract: 1,121,526. Transistor bi-stable circuits. RADIO CORPORATION OF AMERICA. 6 Aug., 1965 [25 Aug., 1964], No. 33862/65. Heading H3T. [Also in Division G4] In a memory arrangement, including at least one insulated-gate field effect transistor, an input terminal 32 is connected to the input terminal of the memory arrangement via the conduction path of an insulated gate field effect transistor 10c The field effect transistors may be of TFT or MOS symmetrical type. If the circuit is storing a binary " 1," then at time t a  (Fig. 2) word source 40 is at zero, transistors 10a, 20b, 20c are ON and 10b, 20a, 10c are biased OFF, making outputs 44, 46 zero and +V. To determine the state of the circuit a read out signal of +V is applied at 38. This turns OFF cross-coupling transistor 20c and the circuit changes state; transistors 10b, 20a, 10c turn ON and transistors 10a, 206 turn OFF so as to make outputs 44, 46 change to +V and zero at time t b . The inter-electrode capacities of the transistors C 2 , C 3  discharge and C 1 , C 4  charge, causing a current IC 1 , 1C 4  through the current sensor 28 which may be a bi-stable or monostable tunnel diode circuit 78-1 (Fig. 3), to indicate that the circuit has switched from the " 1 " state to the " 0 " state and is now storing a binary " 0." To store a binary " 1 " a +V signal is supplied to the digit source 36 together with a + V write signal at 38, this causes symmetrical transistor 10c to turn off and on until the potential at source 14c and gates 16c, 26a rises to +V so as to change the circuit back to its original state, transistors 10a, 20b ON; 10b, 20a, 10c OFF. The write signal then ends at t d  and 38 becomes zero so that transistor 20c conducts to complete the cross coupling circuit and hold the circuit in its original state, storing a binary " 1." Then the digit source signal may become zero without affecting the state of the circuit at t e . If a read out signal of +V is applied at 38 the circuit will change state a second time to store a binary " 0 " and an impulse will again be registered by sensor 28. If the circuit is storing a binary " 0," then the application of a +V read signal at 38 does not change the state of the circuit and no output is obtained from the sensor 28. In a modified circuit (Fig. 5, not shown), further insulated gate field effect transistors (10d 20d) are connected so that read and write signals have to be supplied to 38 and to the interconnected gate electrodes of these transistors in order for the circuit to function. The transistor conductivities may be the reverse to those shown. Memory element.-The bi-stable circuits of Fig. 1 may be arranged in memory planes 70-1-70n (Fig. 3) so that bi-stable circuits 72-1, 72n occupying the same position in each plane each store a different bit of information of a word. - The read and write signals at 38 for circuits of one such word are joined in common at 74 to a word driver 76 and information is read into these circuits from digit driver 77-1- 77n each connected to all the terminals 32 of circuits in that plane 77-1 or 77n. A tunnel diode sensor 78-1 is connected between the supply 30-1, 30n in each plane and the circuits in each plane 70-1, 70n. There may be an array of m by m bi-stable circuits in each plane. In a modification (Fig. 4, not shown), an array of m by m bi-stable circuits (Fig. 5, not shown) are arranged in each plane. For information to be read out or written in from the information source (96-1, 96n) read and write signals must be supplied to (X and Y) inputs of the bi-stable circuits (90-1, 90n) in a common row and column.