Abstract: An out of lock condition is sensed on a data transition by transition basis in clock recovery apparatus. When an out of lock condition is sensed, a range sweeping signal is generated and summed with the correction signal to sweep the frequency of the clock signal over the frequency range of the VCO. When an out of lock condition is absent, i.e., when the VCO is phase locked, simulated data transitions are generated in the frequency/phase detector. An out of lock condition is sensed by a D flip-flop. Data is coupled to the clock input of the flip-flop, the clock signal is delayed by a fraction of its nominal period and coupled to the D input of the flip-flop. The state of the Q output of the flip-flop indicates an out of lock condition.

Abstract: A fiber-optic system includes a photodetector for receiving optical signals from a light source, a threshold producing circuit coupled to the photodetector, and a delay block coupled to the photodetector. The threshold producing circuit produces a decision threshold voltage in response to signals from the photodetector. The delay block, formed of one or more stages of all-pass filter, delays the signals from the photodetector. The outputs of the delay block and the threshold producing circuit are connected to the inputs of a comparator. By providing a delayed signal, the decision threshold voltage is established in the comparator before the delayed signals reach the comparator. In this manner, pulse width distortion is largely eliminated in the first bit of data in burst mode data and the dynamic range of the overall system is preserved. In some cases, a multi-staged delay causes DC offset error in the delayed signal to the comparator.

Abstract: A bipolar transistor amplifier with improved base biasing is disclosed. In the bias circuit of the present invention, the bias current only varies with the log(log) of variations in .beta. of the NPN transistors, making the circuit particularly resistant to temperature and process induced variations in .beta.. A feedback loop also insures that the bias current will remain constant under normal operating conditions. In several embodiments of the present invention, the bias signal and the input signal are kept separate, reducing interference. The amplifier and bias circuit provides a large amount of voltage headroom even with low supply voltages.

Abstract: A light-emitting diode is mounted in the bottom of a cavity in a metal lead and the assembly is potted in a transparent plastic material. The walls of the cavity surround the sides of the light-emitting diode in sufficiently close proximity to effectively shield the light-emitting diode from thermal expansion stresses from the plastic potting material which would induce light output degradation. Such a cavity may be a right-circular cylinder with a diameter less than 75 micrometers greater than the largest transverse dimension of the light-emitting diode. The front face of the light-emitting diode may be flush or beneath the face of the metal lead for minimizing stress. The cavity may be deep enough that the front face of the light-emitting diode is closer to the bottom of the cavity than to its open end. The front face may protrude beyond the open end of the cavity and be surrounded by a reflective surface. The edges of the front face of the light-emitting diode may be beveled for minimizing stress.

Abstract: An electro-optical device with a transparent substrate is produced by epitaxially first growing the device layers, followed by that of the transparent substrate layer on an opaque wafer. The opaque wafer is subsequently removed. The device layers have dopants with sufficient low diffusivities that their electronic characteristics are not adversely affected by long exposure to elevated temperature during the growth of the transparent substrate layer. In a liquid phase epitaxy (LPE) method, a repeated temperature cycle technique is used where the temperature is repeatedly raised up each time after cooling to provide a large cooling range for growing a sufficiently thick substrate layer or a series of device layers. In between growths and during the temperature heat-up periods, the device is stored within the LPE reactor. In other embodimens, the device is either temporarily removed from the LPE reactor or is transferred to another reactor.

Abstract: An optical shaft angle encoder has a plurality of active photodiodes in an array on a semiconductor chip. A rotating code wheel has alternating areas for alternately illuminating or not illuminating the active photodiodes in response to the rotation of the wheel. Errors in the duty cycle involving the end active photodiodes in the array are largely avoided by having a plurality of inactive photodiodes at each end of the array with width and electrical properties effectively the same as the active photodiodes so that leakage current to each end active photodiode of the array is substantially equal to the leakage current to active photodiodes remote from the end of the array. Similarly, leakage current which may affect the duty cycle of individual photodiodes may be minimized by surrounding the individual photodiodes with a reverse biased photodiode junction.

Abstract: A semiconductor light emitting heterostructure device is disclosed. The device comprises an n-type GaAs substrate, a first n-type laeyr of AlGaAs adjacent to the substrate, a second p-type light emitting AlGaAs layer adjacent to the first layer, and a third p-type AlGaAs layer suitable for bonding to an aluminum contact. The device starts with an n-type substrate which is more readily available and has a p-side up configuration which is more suitable for bonding to an aluminum contact.

Abstract: In a light emitting diode comprising a plurality of layers deposited on a substrate, the substrate is etched so as to reduce the area in which the substrate is attached to the plurality of layers. The reduction in the area of attachment results in less light being absorbed by the substrate and thus more total light shining forth from the light emitting diode.

Abstract: A power supply circuit for an LED print head has a reference current source connected to a printer system reference voltage for providing a second reference voltage for an individual, integrated circuit chip. A plurality of substantially similar field effect transistors have their gates connected to the chip reference voltage for providing substantially similar current to each of a plurality of light emitting diodes. The current is enabled to each such LED by the presence or absence of a data signal. A reference resistor in the reference current source permits adjustment so that each of a plurality of integrated circuit chips can provide substantially similar current to each of a plurality of LED dice, or adjust the current level, if required, to achieve similar light output from each LED.

Abstract: A method and an apparatus for measuring settling characteristics of a device under test. A measurement system for measuring an input signal by sampling and digitizing that input signal is employed to obtain reference data by measuring a reference signal, at least one level of which is flat, and to obtain measurement data by measuring a second signal representing the settling characteristics to be measured but containing an error component due to inclusion of the measurement system itself. The error component is removed from the measurement data by adjusting the timing and level of the reference data relative to those of the measurement data.

Abstract: A floating driver circuit. A power supply is connected through a signal source to an amplifier's input terminal. The power supply is also connected to a pair of power supply terminals of the amplifier, via at least one resistor for each power supply terminal, so that direct current flows from the power supply into the power supply terminals. Further, at least one capacitor is connected to each power supply terminal. A cable, preferably coaxial, has first and second conductors. The first conductor is connected to a signal output terminal of the amplifier. The second conductor is connected to the power supply terminals through the capacitors. A pair of these circuits is combined at opposite ends of an electrical component to enable measurement of the impedances thereof.

Abstract: The nitrogen-selectivity of an atomic emission detection system is enhanced by use, as the reagent gas, of a single gas or a mixture of gas components containing oxygen and hydrogen in an oxygen/hydrogen molar ratio of about 1:10 to 10:1.

Abstract: A remote calibrated power source system comprises an instrument for generating power, the instrument being positioned at a first location, and a remote calibrated power source module for outputting calibrated power, the remote module being positioned at a second location that is removed from the first location. The remote module includes power sampling means for sampling the power generated by the instrument and generating a sampled voltage, the power sampling means having inherent frequency errors, a compensation circuit for generating a frequency-varying correction voltage, and summing amplifier means for receiving both the correction voltage and the sampled voltage and generating a compensated sampled voltage.

Abstract: A retaining and locking clamp, mounted onto a first apparatus, for retaining and locking a second apparatus to the first apparatus. The first apparatus has a plate which in turn includes an aperture. The clamp comprises an inner rod that has a first end portion and a second end portion, the second end portion being adapted to be received within the aperture of the first apparatus plate so as to mount the inner rod to the first apparatus. The clamp also includes an outer sleeve that is rotatably mounted onto the inner rod, the outer sleeve has a retaining and locking flange and a surface. The clamp further comprises a turn knob that is rotatably mounted onto the inner rod, the turn knob has a surface that is adapted to frictionally engage the outer sleeve surface, whereby rotating the turn knob causes the turn knob surface to frictionally engage the outer sleeve surface so as to permit the outer sleeve flange to retain the second apparatus.

Abstract: An automatic spectrum analyzer is provided with enhanced features for measured data handling and analysis. One feature allows the user to establish a sequence of operations to be performed at the end of each sweep of the instrument. Another feature enables the user to specify a particular signal amplitude and to have a marker placed on a displayed signal trace at that amplitude. Still another feature provides a marker that can be positioned on the next signal peak to the right or the left of the current marker position, enabling the display of the amplitude and frequency of the signal on which the marker is placed.

Abstract: An automatic spectrum analyzer is provided with enhanced features for measured data handling and analysis. One feature allows the user to establish a sequence of operations to be performed at the end of each sweep of the instrument. Another feature enables the user to specify a particular signal amplitude and to have a marker placed on a displayed signal trace at that amplitude. Still another feature provides a marker that can be positioned on the next signal peak to the right or the left of the current marker position, enabling the display of the amplitude and frequency of the signal on which the marker is placed.

Abstract: A method and apparatus for using an AC detection network analyzer with either a pulsed RF or a CW source signal is disclosed. An AC/DC detector is placed between an AC detection network analyzer and a device under test. If a source signal is a pulsed RF signal the AC/DC detector can be switched to transform the pulsed RF signal to produce an AC signal for the network analyzer. If the signal source is a CW signal, the AC/DC detector can be switched to rectify the CW signal, modulate the CW signal, sample the CW signal, and filter the CW signal. This will also produce the AC signal for the network analyzer.

Abstract: A method of fabricating sub-micrometer gates in a semiconductor device is disclosed in which a pre-passivation layer is formed over the gate region during fabrication. This pre-passivation layer protects the gate and underlying gate trough region from surface contamination during device fabrication. Sub-micrometer gate lengths are obtained by use of optical lithography, e.g., angle-shadow metal evaporation techniques and chemical lift-off methods.

Abstract: A water faucet is disclosed that is automatically turned on and off in response to the proximity of the user's hand or other object to the faucet. An ultrasonic transducer is located in the faucet near the water outlet and transmits bursts of ultrasonic waves. When a wave reflects off a user's hand and creates an echo signal, the echo is detected by the ultrasonic transducer. Circuitry connected to the ultrasonic transducer determines when an object is within a predetermined distance of the faucet by measuring the time elapsed between the transmission of the burst and the reception of the echo. Once an object is within this predetermined distance, the circuitry causes a valve to open and water is supplied by the faucet.

Abstract: A high accuracy pen plotter includes an automatic sheet feeder for feeding individual sheets of paper from a paper tray to a platen for plotting. A microprocessor, various stepper motors and encoders allow for accurate and repeatable positioning and alignment of the sheet of paper to be plotted. The sheet of paper is automatically fed from the tray to the platen, is pulled entirely free from the tray, is aligned against a reference edge and may be forcefully ejected from the plotter after plotting is finished.