Abstract: A battery backup circuit for an MOS memory which has a multiplexed pin (WE) that functions to provide backup power to a memory cell array (50) upon loss of primary power V.sub.cc. A voltage comparator (10) detects when the primary power V.sub.cc becomes less than the backup voltage on the WE terminal. Upon detection of loss of primary power the memory cell array (50) is powered by a connection to the WE terminal. A primary power status signal (POK) indicates the status of the primary power and is driven to a state indicating insufficient circuit voltage for normal operation when V.sub.cc drops below an acceptable limit or when there is inadequate substrate bias. The circuit of the present invention further generates an inhibit signal to prevent the operation of peripheral circuits (70) to write data into the memory cell array (50) upon detection of a failure of primary power. The inhibit signal is generated when primary power is lost or when the substrate bias is inadequate.

Abstract: Block redundancy is utilized to improve yield and lower die cost for an electrically programmable read only memory (EPROM). The EPROM is organized 8Kx8 with four primary memory blocks on each side of a central row decoder. Each block includes an array of memory cells, column select, column decode, sense amp, data buffer and other overhead circuitry. One block of redundant circuitry is also provided for each set of four blocks and includes a redundant memory matrix, a redundant column decoder, a redundant column select, a redundant sense amp and a redundant data buffer. Incorporated within each primary memory block is a multiplex logic circuit which is independently programmable to selectively disconnect the associated primary memory block and substitute the redundant memory block, including the redundant column decoder, column select, sense amp and data buffer.

Abstract: A MOSFET random access memory having an extremely low current load memory cell is disclosed. The memory cell comprises a cross-coupled binary stage in which one or more paths to ground can be selectively switched on or off through true and complement data nodes. Impedance means connect a power supply node to the data nodes for charging the data nodes to predetermined voltage levels. The impedance means comprise an intrinsic-extrinsic junction of a substantially pure, intrinsic semiconductor material and a diffusion of extrinsic conductivity impurities disposed within a region of the intrinsic semiconductor material. The impedance means is formed by an isoplanar silicon gate process as an integral portion of a polycrystalline silicon strip which interconnects the power supply node to a data node. A portion of the polycrystalline silicon strip is extended from the data node to form the gate of the transistor to which it is cross-coupled.

Abstract: A method for making a semiconductor device is described in which polycrystalline silicon is vacuum deposited and then converted to silicon dioxide thereby providing a number of advantages over direct deposition of silicon dioxide. The method has particular applicability to isoplanar MOSFET integrated circuit manufacturing.

Abstract: A switch for selecting internal circuit options in MOS/LSI circuits without altering the circuit layout on a semiconductor chip by selectively implanting channels of field-effect transistors such that selected circuit-option lines are coupled to a designated line. Switches may be constructed with multiple inputs and a single output, or with multiple outputs and a single input, or with multiple inputs and multiple outputs. A bidirectional switch may also be constructed by controlling the gate potential of each transistor connecting one of the option lines to the designated line with a two-input switch for selecting either a high or a low gate potential.

Abstract: A method for making a semiconductor device is described in which polycrystalline silicon is vacuum deposited and then converted to silicon dioxide thereby providing a number of advantages over direct deposition of silicon dioxide. The method has particular applicability to isoplanar MOSFET integrated circuit manufacturing.

Abstract: A dynamic random access read/write memory having 4,096 binary storage cells is disclosed. The system utilizes a single set of six address input buffers and one decoder for both row and column address information. The memory array includes two 32.times.64 arrays of dynamic storage cells separated by a row of 64 sense amplifiers each having split sense buses or digit lines extending to each column of memory bits. The decoders are disposed along one edge of the array which is at right angles to the row of sense amplifiers. The column enable lines from the decoders extend through the memory array between parallel row enable lines and then turn and proceed as a different level of interconnect between parallel digit lines to select the addressed sense amplifiers. Each column enable line enables two sense amplifiers which simultaneously read data from two cells of the addressed row.

Abstract: A read only memory (ROM) structure in which a plurality of enhancement and depletion transistors are organized into a series-connected NAND logic matrix. The usual metal-to-diffusion contacts required for every one or two bits, as well as interweaved power supply lines required for every two row lines in conventional NOR logic circuits are not used in the series arrangement thereby minimizing the geometry of the ROM structure. In a preferred embodiment, logical information is stored within the ROM matrix by means of silicon gate metal oxide semiconductor field effect transistors which are arranged into a matrix having a number of common gate input rows and a number of series connected output columns which correspond to selected logic combinations of the inputs. The logical content of individual memory cells within the matrix is determined by providing either enhancement mode or depletion mode MOSFET transistors as elements of the matrix.

Abstract: Threshold voltage regulation of field-effect transistors on a common substrate of an integrated circuit is achieved by adjusting the back bias on the substrate using a charge pump that is selectively operated whenever the threshold voltage of a designated enhancement mode FET falls below a reference voltage. A voltage divider provides the reference voltage that is applied to the gate of the enhancement mode FET, which when turned-on enables the charge pump.

Abstract: An MOS integrated circuit includes internal circuitry for detecting the voltage level of an external power supply. The internal circuitry comprises networks for producing two reference voltages, each of which varies with supply voltage in a different but predictable manner such that when the reference voltages are equal, the supply voltage is at a sufficiently high level to assure the generation of valid logic levels. As the supply voltage increases beyond such level, the two reference voltages diverge in value, detection of which is achieved with a different amplifier. Circuitry responsive to the output of the differential amplifier gives a positive indication of sufficient supply voltage to other circuit portions of the integrated circuit device.

Abstract: The invention disclosed herein is a high performance inverter circuit using MOSFETs having varying threshold voltages produced by selectively varying ion implantation doses in the channels of the MOSFETs and using a slightly depletion type MOSFET, rather than a conventional depletion type, in the output stage.

Abstract: A symmetrical structural layout for the principal components of each cell in a group of four mutually contiguous cells of an array of memory cells is disclosed. A common drain supply node is centrally disposed within the group and is coincident with the intersection of first and second mutually perpendicular axes of symmetry. Corresponding components of contiguous cells in each row and column are symmetrically disposed with respect to each of the first and second axes of symmetry. In a preferred embodiment, the principal components of each cell include a plurality of insulated gate field-effect transistors each having a source diffusion region and a drain diffusion region formed within the substrate and a plurality of impedance devices electrically connecting the common drain supply node to the drain diffusions of the transistors in each cell.

Abstract: An input buffer for MOSFET integrated circuit for receiving low level voltage signals even below the threshold voltages of the transistors comprising the circuit is described. A reference voltage between two logic levels of the input voltage, such as TTL logic signals of 0.8 volts and 1.8 volts, is trapped on a reference storage node and the logic input voltage is trapped on a data input storage node. The two trapped voltages are then capacitively boosted by the same voltage to a level well above the transistor threshold voltage so that the differences in the voltage levels can be amplified, and the logic signal latched up by conventional circuitry. The voltage levels need be only momentarily boosted above the threshold level.

Abstract: An integrated circuit MOSFET dynamic random access memory is disclosed which utilizes a plurality of memory cells arrayed in rows and columns. One-half of the cells in each column are connected to a true digit line and the other half are connected to a complement digit line. The true and complement digit lines are each connected through a separate transistor, which functions as a varible resistance, to true and complement input nodes of a sense amplifier. The sense amplifier is comprised of a transistor connecting each input node to a latch node, with the gates of the transistors cross coupled to the opposite input nodes. The digit lines are precharged to equal voltages corresponding to V.sub.DD. When enabled by an address signal, a storage cell is connected to one of the digit lines at the same time a dummy cell is connected to the other line. As a result, one of the digit lines has a slightly higher voltage than the other.

Abstract: A dual-tone multiple frequency signal generator is provided for use with telecommunications systems, data transfer systems and other applications. The tone encoding system utilizes MOS/LSI integrated circuitry on a single chip powered directly by telephone line voltages. An electronic keyboard circuit provides synchronized pulses to decode single-pole, single-throw keyboard switches by row and column. A crystal-controlled oscillator generates a reference frequency which is divided according to the row and column of an activated keyboard switch to obtain two pulse signals having frequencies representative of the activated switch. The outputs of the divider circuitry are fed to programmed logic array which generates two digitally coded signals each representing a sinusoidal waveform. A digital-to-analog ladder network converts the digitally coded signals to continuous sine waves, and an operational amplifier combines the sinusoidal waveforms to provide a dual-tone output.

Abstract: An integrated circuit MOSFET dynamic random access memory is disclosed which utilizes a plurality of memory cells arrayed in rows and columns. One-half of the cells in each column are connected to a true digit line and the other half are connected to a complement digit line. The true and complement digit lines are each connected through a separate transistor, which functions as a variable resistance, to true and complement input nodes of a sense amplifier. The sense amplifier is comprised of a transistor connecting each input node to a latch node, with the gates of the transistors cross coupled to the opposite input nodes. The digit lines are precharged to equal voltages corresponding to V.sub.DD. When enabled by an address signal, a storage cell is connected to one of the digit lines at the same time a dummy cell is connected to the other digit line. As a result, one of the digit lines has a slightly higher voltage than the other.

Abstract: A MOSFET random access memory having a highly sensitive sense amplifier is disclosed. The sense amplifier utilizes a field effect transistor connected in the common gate mode so as to produce a large output swing on a reltively low capacitance output node, which is the drain node of the transistor, as a result of a relatively low voltage swing produced by reading data stored in a memory cell on a high capacitance column bus connected to the source of the transistor. The sense amplifier is shown in differential configuration with a low power level shifting circuit and also with both static memory cells, where a greatly improved access time is produced, and with destructive readout cells where improved reliability is possible.

Abstract: A clock generator for an MOSFET integrated circuit having a plurality of cascaded delay stages is disclosed. Each delay stage includes a bootstrap inverter having first and second transistors connected in series between the drain supply voltage and a source supply voltage, thus forming a first node between the transistors. The first node is capacitively coupled to a bootstrap node which is connected to the gate of the first transistor. The bootstrap node is also coupled through the channel of a third transistor to an input. The gate of the third transistor forms a third node. Circuit means are provided for precharging the third node and then isolating the third node while an input signal is applied through the third transistor to the bootstrap node so that the third node is also bootstrapped up to permit rapid charging of the bootstrap node to the full voltage of the input signal.

Abstract: A trinary input circit for an MOSFET integrated circuit includes a biasing stage formed by using a standard inverter, whose output is connected to its input so as to establish a particular bias voltage level when the input to the trinary input circuit is left floating. The output of the biasing stage is applied to the inputs of a second inverter stage having a higher beta ratio than the bias stage and to the input of a third inverter stage having a lower beta ratio. The bias stage when left open circuited will seek a quiescent voltage which is above the switching threshold of the second stage and below the switching threshold of the third stage. Thus, as a result of the relative beta ratios of the three stages when the input to the bias stage is left open, the bias stage will seek a particular voltage level such that the high beta ratio stage produces a logic 0 output and the low beta ratio stage produces a logic 1 output.