Abstract: A carrier detection circuit includes a rectification stage, an integrator, a comparator, and a digital counter. By utilizing a digital counter, long time constants are provided without the use of external components. If desired, a mark detect circuit is used when a mark must be present to signify the presence of carrier. Hysteresis is provided by the comparator to insure that slight fluctuations in the carrier level do not affect the comparison.

Abstract: In one embodiment of this invention, a uniquely designed switched capacitor multiplier/adder (129) is provided which also functions as a digital-to-analog converter in a single subcircuit. The multiplier/adder, in a single operation, multiplies an analog voltage by a binary coefficient, and sums this product with a second analog voltage. The use of this unique subcircuit significantly reduces the space requirements for the construction of, for example, a speech synthesis circuit utilizing linear predictive coding over prior art circuits. This invention provides a novel structure and method which minimizes error components in the synthesized speech signal due to voltage errors inherent in the use of analog sample and hold circuits which are used to store the forward and backward prediction errors utilized in the linear predictive coding technique. Using the method of this invention, the inherent error components are alternatively inverted and not inverted upon each clock cycle of the multiplier/adder.

Abstract: A method for fabricating an integrated circuit semiconductor device comprised of an array of MOSFET elements having self-aligned or self-registered connections with conductive interconnect lines. The method involves the formation on a substrate of a thick oxide insulation layer surrounding active area openings. A gate electrode within each opening is utilized to provide self-registered source and drain regions. In two embodiments, the gate is covered on all sides and on its top surface with a protective layer of nitride or thick oxide. In one of the embodiments, after the formation of the source-drain regions a relatively thin protective layer of etch stopper is applied to the entire chip prior to the application of an upper insulative layer.

Abstract: A late mask programming process is provided for factory programmed ROMs or logic circuitry. MOS transistors functioning as ROM cells or in logic circuitry are fabricated by a standard MOS Process. Then, a thin stop layer of silicon nitride is provided over the transistors followed by a layer of silicon dioxide. Programming is accomplished by applying a program mask and etching through the layers overlying the gate regions of selected transistors down to the silicon nitride stop layer. The silicon nitride stop layer prevents overetching and shorting of the gates. Then, ions are implanted underneath the gates of the selected MOS transistors to alter their threshold so, for example, as ROM cells they signify a different state than those cells whose transistor gates are not implanted with ions. The silicon nitride layer serves to stop the etch solution but permits the ions to pass through, penetrate the substrate and raise the thresholds of the selected transistors.

Abstract: An operational amplifier has one noninverting input lead (116), and two inverting input leads (117a, 117b). One of these inverting input leads (117a) is utilized to compensate for the effects of the inherent offset voltage (V.sub.off) of the operational amplifier, and the second inverting input lead (117b) receives an input signal to be amplified or compared.

Abstract: A unique fabrication method allows the formation of regions of opposite conductivity types in a semiconductor substrate 100 utilizing a single masking step. A first mask is formed on the surface of the semiconductor substrate and patterned to define the regions (110) which are to be doped to a first conductivity type. Subsequent to the doping of these first regions, a protective layer (111) is formed over these first regions. The mask is then removed, thus exposing the regions (112) which are to be doped to the second conductivity type opposite to said first conductivity type. These exposed regions are then doped to said opposite conductivity type, with the first regions which have been doped to said first conductivity type protected by said protective layer.

Abstract: A switched capacitor gain stage (110, 120) having a programmable gain factor. This gain factor is determined by the connection of desired gain determining components (14-17; 25-28) contained within a component array (100, 101). A sample and hold circuit (46) is provided for the storage of the error voltage of the entire gain-integrator stage. This stored error voltage (V.sub.error) is inverted and integrated one time for each integration of the input voltage (V.sub.in), thus eliminating the effects of the inherent offset voltages of the circuit from the output voltage (V.sub.out).

Abstract: A unique dynamic operational amplifier is constructed utilizing a switched capacitor (25) as the biasing means, wherein the switched capacitor biasing means is capable of effectively doubling the power supply voltage supplied to the dynamic operational amplifier, thus greatly extending the range of the input voltage (V.sub.IN) and output voltage (V.sub.OUT) of the dynamic operational amplifier.

Abstract: A digital to analog converter (100) utilizes a current mirror connected to a reference voltage (V.sub.REF) to generate a constant reference current (I.sub.REF). A voltage divider (R.sub.1 and R.sub.2) is used in conjunction with a plurality of MOS transistors (X.sub.1 -X.sub.N) serving as current mirrors having specific current carrying capabilities which are controlled by selected binary digits (bits) of a digital signal. By the appropriate connection of desired ones of said plurality of MOS transistors, a specific fraction of said reference current is caused to flow through said plurality of MOS transistors. The amount of current flowing through said plurality of MOS transistors generates an output voltage (V.sub.OUT) from the digital to analog converter of this invention. This output voltage may be positive or negative with respect to the reference voltage, thus the output voltage is bipolar.