Abstract: An amplifier with variable gain which maintains high Q when saturated. A resonant circuit is connected between collector outputs of a differential pair of transistors and RF chokes couple DC supply current to the transistors. The chokes have a high impedance at the desired frequency. The emitters of the differential pair of transistors couple together to form a common output which is connected to a current source. The amount of current from the current source substantially controls the gain of the amplifier. Because the resonant circuit is not shunted with a low impedance even when one of the transistors saturates, the Q of the resonant circuit is maintained.

Abstract: A high-speed driver for LED data communications systems. A differentiator provides a turn-on and a turn-off pulse of current to the LED. The amount of charge delivered during turn-off is adjusted to sweep substantially all of the carriers from the LED without reverse-biasing the LED.

Abstract: An arrangement for tuning a data filter in a mass storage system. The filter cutoff frequency (low pass) may be set as a percentage above or below the incoming data rate to achieve the desired "eye opening" in read data. The frequency of a reference oscillator in a phase-locked-loop (PLL) and the cutoff frequency of the filter is controlled by a common control signal from the PLL. The PLL, locked to a scaled multiple of the data rate, determines the cutoff frequency of the filter.

Abstract: An optical power monitoring circuit in an optical data receiver. A transconductance amplifier with non-linear feedback converts averaged photodiode current into a voltage representing a logarithm of the received optical power, which may be converted into decibels referenced to a standard power (dBm). The circuit has wide dynamic range and uses matched devices to provide processing and temperature compensation.

Abstract: A differential line driver with small common mode shift when going inactive. Two pairs of serially coupled switches diagonally switch when sending data. All switches close when the driver is disabled, the common mode output voltage being established by resistors serially disposed between the pairs of switches and the power source therefore.

Abstract: A lateral MOS-controlled thyristor (MCT) structure using a single MOS gate for both turn-on and turn-off. By eliminating a parasitic lateral PNP transistor, through the addition of a high resistivity region surrounding one output terminal, and adding a DMOS transistor to a conventional thyristor structure, the maximum turn-off current limit is increased with lower forward voltage drop than that available in prior art lateral MCTs.

Abstract: A process for growing selective epitaxial layers on a silicon substrate. In a epitaxial growth reactor, hydrogen and the reactive gasses, the silicon source gas and hydrochloric acid, are introduced. The amount of silicon to free hydrochloric acid is controlled to be about 1:6 during the growth process and then turned off, the hydrogen remaining on. The resulting epitaxial layer may be grown over one micron in thickness with less than 0.1 micron of faceting. Further, a etchant of H.sub.2 O and HF diluted in NHO.sub.3 is first used to remove surface damage on the silicon substrate prior to epitaxial layer growth.

Abstract: An FET with multiple channels to provide a substantially linear transfer characteristic. The widths and carrier concentrations of the channels, and the depths of the channels below the gate of the FET, are adjusted such that a substantially linear gate voltage-to-output current (drain) transfer characteristic of the FET results. In addition, the electrical characteristics of the FET may be adjusted by changing the spacing of the drain and source diffusions from the gate.

Abstract: A peak detector for rapidly following the peak voltage of a pulsed input signal without significant droop between pulses. The peak detector has a master section which selectively controls the droop rate of a slave section. The output of the slave section is the output of the peak detector. The master section droop is determined by a resistor, which may be disconnected therefrom to hold the peak of the input signal.

Abstract: A mobile ion getterer is added to metalization layers on an integrated circuit or discrete device to reduce mobile ion contamination therein. Preferably, chromium is used as the mobile ion getterer and is added to an aluminum target used as the metal source for sputtering the chromium and aluminum onto the integrated circuit or discrete device. This technique removes the need for ultrahigh purity aluminum conductors or gettering material (P-glass) in contact with the metal conductors. This technique may be used with virtually all metalization apparatus and processes used for depositing metal onto semiconductor devices.

Abstract: An FET with multiple channels to provide a substantially linear transfer characteristic. The widths and carrier concentrations of the channels, and the depths of the channels below the gate of the FET, are adjusted such that a substantially linear gate voltage-to-output current (drain) transfer characteristic of the FET results. In addition, the electrical characteristics of the FET may be adjusted by changing the spacing of the drain and source diffusions from the gate.

Abstract: A solid-state relay with delayed turn-on time without substantially increasing the time to bring the relay to full conduction after the delay. A current limiter disposed in series with photodiode array limits current therefrom to delay turn-on until the gate voltage of the output transistors is approximately the threshold voltage thereof. Once the threshold voltage is reached, the current limiter is bypassed so that the photodiode array provides full current to quickly turn-on the output transistors.

Abstract: An amplifier circuit for use as a unity gain buffer or an input stage in a current-mode feedback amplifier. As a unity gain buffer, the circuit has very low output impedance and wide dynamic range while having low offset. As an input stage, the circuit has a very low impedance inverting input and a high impedance non-inverting input with wide dynamic range and low offset. The circuit has two mirror image halves, each half having four transistors of the same polarity type and a current mirror. Each half is biased by a current source, the sources having nearly identical current.

Abstract: A digital squelch circuit for detecting valid data signals in a burst mode communication system, such as a packet-based local area network. Transitions in the input signal to the squelch circuit start a counter which asserts at least one signal a predetermined time from the transition. The absence or presence of the signal when the next transition in the input signal occurs determines if the frequency of the input signal is less than or greater than a frequency related to the predetermined time interval. When a predetermined number of transitions meeting the desired frequency requirement are received, the input signal is judged valid.

Abstract: A high voltage capacitor structure for integrated circuits or the like. The capacitor includes a provision for equalizing charge when multiple capacitors are series coupled. Charge is equalized by a SiN layer overlaying, and in contact with one terminal of, the capacitor. A ground ring surrounds the capacitor structure and is also overlayed by, and in contact with, the SiN layer.

Abstract: A process for growing selective epitaxial layers on a silicon substrate. In a epitaxial growth reactor, hydrogen and the reactive gasses, the silicon source gas and hydrochloric acid, are introduced. The amount of silicon to free hydrochloric acid is controlled to be about 1:6 during the growth process and then turned off, the hydrogen remaining on. The resulting epitaxial layer may be grown over one micron in thickness with less than 0.1 micron of faceting. Further, a etchant of H.sub.2 O and HF diluted in NHO.sub.3 is first used to remove surface damage on the silicon substrate prior to epitaxial layer growth.

Abstract: A circuit technique for reducing the sensitivity of solid-state relays, having a normally-on (closed) contact, to transients on the output thereof when the contact is open (relay is actuated). The relay has series of photodiodes, a switch, and a pair of depletion type output transistors coupled to the output of the relay. The output transistors are driven by the photodiodes with the switch in parallel with the input of the transistors. The switch allows for the rapid deactuation of the relay. A resistor, disposed in series with the switch, reduces the susceptibility of the relay to the transients by slowing the turn-on of the switch.

Abstract: An emitter-coupled logic (ECL) buffer circuit using two differential pairs of transistors to limit the output voltage of the buffer to ECL signal levels. A first differential pair of transistors couples the current from a first current source to load resistors in the buffer, thereby establishing the output voltage for the logical "low" output. The second differential pair couples the current from a second current source, having a current less than the current from the first current source, to the load resistors to establish the output voltage for the logical "high" output.

Abstract: The mobility of a relatively narrow bandgap semiconductor material can be significantly enhanced by incorporating it into a multilayered structure (10) comprising a first plurality of relatively narrow bandgap layers (12) of the material and a second plurality of wider bandgap semiconductor layers (14) interleaved with and contiguous with the first plurality. The wide bandgap and narrow bandgap layers are substantially lattice-matched to one another, and the wide bandgap layers are doped such that the impurity concentration-thickness product therein is greater than the same product in the narrow bandgap layers. The fabrication of the structure by MBE to enhance the mobility of GaAs is specifically described. In this case, the narrow bandgap layers (12) comprise GaAs and are unintentionally doped to about 10.sup.14 /cm.sup.3, whereas the wide bandgap layers (14) comprise AlGaAs doped n-type to about 10.sup.16 to 10.sup.18 /cm.sup.3. The incorporation of this structure in an FET is also described.

Abstract: Differential amplifier having multiple stages, each stage having the gain thereof set by digital control. The gain of each stage is individually controlled, thereby allowing wide dynamic range and gain. Each stage has a differential pair with multiple sets of gain-setting resistors in the emitters of the pair. By selecting which resistor set, or combination of resistor sets, is used, the gain of the stage is controlled. The result is a 4 stage, 0-45 dB gain amplifier for RF or IF applications, with the gain adjustable in 3 dB increments.