Abstract: An IC chip having a Zener diode with a subsurface breakdown junction to assure stable operation. The diode is formed by a triple diffusion process compatible with conventional bipolar processing. A deep p.sup.++ diffusion first is applied, reaching through the epitaxial region to the buried n.sup.+ layer; next, a shallow p.sup.+ diffusion is formed over the deep p.sup.++ diffusion and extending laterally beyond that diffusion; finally, a shallow n.sup.+ diffusion is applied over the p diffusions, to form a subsurface breakdown junction therewith. The topology of the mask windows is selected to provide concentration profiles which insure that the breakdown occurs at the subsurface junction, and that other desirable diode characteristics are achieved.

Abstract: An integrated-circuit 12-bit digital-to-analog converter comprising binarily-scaled constant-current sources with associated switch cells employing bipolar transistors to direct the bit currents either to a summing bus or to ground. The switch cells include a first differential transistor pair to translate a single-ended binary logic signal to double-ended (balanced) format, and a second, fully-balanced differential pair operated by the balanced logic signal to direct the bit current correspondingly. A bias-generating circuit maintains a constant collector-base voltage at the constant-current source. The threshold voltage for the logic signals can be set for TTL logic or, by pin-programming, for CMOS logic of either low-voltage or high-voltage type.

Abstract: An integrated circuit two terminal temperature transducer providing an accurate current output that is linearly related to absolute temperature over an extended temperature range. The circuit is of the type using first and second transistors having conductive areas of different sizes, and control transistors for supplying equal currents through the first and second transistors to operate them at different current densities, and a resistor responsive to the base-to-emitter voltages of the first and second transistors for developing currents therethrough proportional to absolute temperature. Improved accuracy over an extended temperature range is provided in a two terminal device by means of a third transistor coupled to the first and second transistors to generate another controlled current varying linearly with absolute temperature to be combined with the currents through the first and second transistors to form an output current.

Abstract: A protective case for an electrical instrument on a circuit board, arranged to mount the instrument upon a panel in an opening provided therein. The case is characterized by a housing having an end opening for introduction of the circuit board therein and a snap-in mounting structure for automatically and securely mounting a circuit board within the housing. The mounting structure includes means forming a ledge, provided for example by four corner platforms molded into the housing, for supporting one side of the circuit board. Two pairs of opposed resilient fingers, preferably molded integrally with the walls of the housing, extend with an inward cant along the path of the circuit board from opposite interior sides of the housing to be flexed outwardly by the edges of the circuit board as it is introduced into the housing.

Abstract: An enclosed modular circuit component is immobilized against deleterious movement due to high impact, shock and vibration movement. A two-piece enclosure case for securely immobilizing a wide variety of readily available modular circuit components is easy to fabricate and utilize with the components. The enclosure case comprises two halves each of which has a top and a bottom, respectively, with two oppositely disposed side walls projecting therefrom. At least one half of the case has a ledge upon which the circuit component header, such as an element support board or a printed circuit board, may be supported. The other half of the case is then provided with means to urge the board against the ledge so that when the two halves are placed together the component is sandwiched between them in a secured immobile relationship. The component elements may be maintained spaced from contact with the enclosure interior surfaces.

Abstract: An isolation amplifier comprising three separate, conductively-isolated sections: (1) an input section including an AC modulator, (2) an output section including a demodulator, and (3) an oscillator section. The AC signal from the oscillator section is transformer-coupled to the modulator section to provide the AC carrier excitation for the modulator and also to energize a rectifier power supply circuit to produce DC voltages for the active elements of the input section. The modulated carrier signal developed by the modulator section is transformer-coupled to the demodulator section. Each of the transformers includes two separate cores which are coupled inductively by single-turn windings. Special electrostatic shielding is provided to reduce leakage effects.

Abstract: A digital-to-analog converter the output circuit of which comprises a set of switching transistors arranged as current generators. The currents through the switching transistors are maintained constant by means of a supply voltage adjusting circuit comprising a separate reference transistor matched to one of the switching transistors and energized by the same voltage supply lines as the switching transistors. The supply voltage adjusting circuit includes an operational amplifier which senses the collector current of the reference transistor, and adjusts the supply voltage so as to maintain that collector current constant. This automatic adjustment of the supply voltage also maintains the current through the switching transistors constant.

Abstract: An analog-to-digital converter of the ramp-integrator type utilizing a special technique to reduce errors due to offset voltages. The integrator first is ramped up and then back to a reference level, by sequential application of opposite-polarity reference signals. A digital determination of net offset error then is made by comparing the total time of ramp-up-and-back with a fixed time period set by a clock generator. During the subsequent conversion operation, integration of the analog signal is controlled in accordance with the amount of net offset error so as to provide a feed-forward error correction. Integration is always in the same direction away from zero for analog signals of either polarity, thus avoiding the effects of discontinuity around zero input.