Abstract: A differential amplifier includes two amplifier halves each including a feedback transistor for providing closed-loop gain, for driving a common load impedance, and for providing a differential current output. Each amplifier half further includes a first feedback path operable in a normal operating condition and a second feedback path operable in an overdrive condition. The first feedback path consists of first and second diodes connected between an emitter of the feedback transistor and a voltage input of the differential amplifier. A junction between the first and second diodes is coupled to the common load impedance. The second feedback path consists of a third diode connected between the emitter of the feedback transistor and the second voltage input, such that the differential amplifier and the feedback transistor remain operational and electrically isolated from the load impedance during the overdrive condition.

Abstract: A resonance compensated unity voltage gain amplifier comprises an input stage and an output stage connected in feedback to the input stage and a series resonance circuit for compensating for the resonance of the output and input stages created by the feedback. Reactance of the series resonance circuit is adjusted to be substantially zero at the resonant frequency of the amplifier. The resonance compensated amplifier is incorporated into a gain selectable amplifier. The resistance on the output stage of the amplifier across which the input voltage is applied via the output voltage may be selectively varied to change the current gain of the amplifier.

Abstract: An integrated circuit is mounted on the front face of a substrate of dielectric material and the substrate is fitted in an aperture that extends through a circuit board. The substrate has contact elements distributed about the periphery of its front face, and the circuit board has corresponding contact elements on its front face distributed about the periphery of the aperture. A first clamping member is positioned at the back face of the circuit board so as to extend over the aperture in the circuit board. The first clamping member is made of thermally-conductive material and is in thermally-conductive contact with the back face of the substrate. A second clamping member is positioned at the front face of the circuit board and extends at least partially over the peripheral area of the front face of the substrate. A resilient member is effective between the second clamping member and both the substrate and the circuit board.

Abstract: A DC level shift circuit includes a differential amplifier with a level shift stage. The level shift stage has two portions for transmitting the input signals forming the differential signal through the level shift stage. A current source transmits the input signals through the level shift stage. Transistors with impedances substantially equal to the current source impedances are cross coupled to each input terminal. Each transistor senses a distortion signal produced by the current source impedance at one terminal and produces in response a correction signal. The correction signal is then transmitted to the other input terminal to be summed with the distortion signal there to pass the input signals through the level shift stage without distortion. The DC level shift stage is also responsive to another correction signal generated by a feedback control stage to control the common mode voltage of the amplifier.

Abstract: A precision differential amplifier having unity-gain buffer amplifier input stages on each side of the amplifier includes a primary feedback path between the collector and base of the inside buffer amplifier transistor which operates when the differential amplifier is operated within its linear operating range. Under an overdrive signal condition, the primary feedback path is opened and a secondary feedback is activated to control the collector and base of the inside buffer amplifier transistor, thus preventing saturation of the inside buffer amplifier transistor and cutoff of the outside transistor. The primary and secondary feedback paths consist of only semiconductor junctions, minimizing heat and loading effects, reducing power supply voltage requirements, and facilitating rapid overdrive recovery.

Abstract: An active low-pass filter especially suitable for inclusion in an integrated circuit and capable of operating at frequencies up to at least f.sub.T /.beta. of transistors within the filter. A bootstrap circuit is coupled to the emitter follower to reduce the capacitive effect of the emitter follower on the passed signal and to guarantee precision pass band gain match among the filters. A plurality of active filters may be connected across the signal path to provide a selection of bandwidths. A filter is switched into and out of the signal path by selectively enabling and disabling its current source.

Abstract: A beam detection apparatus for sensing the position of an electron beam within a cathode ray tube is disclosed. The apparatus includes a photodetector for optically detecting the intersections of the electron beam with a graticule line on the faceplate of the cathode ray tube. In a second embodiment, an electrically conductive pattern of reference markers is applied to the graticule for intercepting the beam and a detector is coupled to the conductive pattern for detecting the interception. Calibration circuitry is also included to generate input signals to deflection amplifiers coupled to the cathode ray tube and to evaluate detection signals generated by the beam coinciding with a graticule line. The calibration circuitry compares the input signals to the input signal value represented by the graticule line and adjusts the deflection amplifiers of the cathode ray tube accordingly to cause the beam to coincide with a graticule line bearing a predetermined relationship to the input signal deflecting the beam.

Abstract: A voltage-controlled current source produces two output current signals whose difference is linearly related to an input voltage signal. The source includes an input buffer and a reference buffer each coupled separately to a current mirror and also coupled together across a current transmitting resistor. In response to the input voltage signal and current transmitted between the buffers, the current mirrors produce currents that differ in proportion to the difference between the input and reference voltage signals. The current mirrors also reproduce the differing currents in output paths as the output current signals. A fixed current source is coupled to each output path for drawing a fixed current from each path to linearize the current difference.

Abstract: A rotary control having a variable detent is disclosed. The control, for electrical instruments and the like, includes a manually rotatable shaft to which a plate is coaxially mounted. The plate includes magnetizable flutes extending radially therefrom, each flute corresponding to a rotational stop position of the rotary control. Spaced adjacent the plate is a switchable electromagnet that forms a detent. A control switch in communication with the electromagnet selectably energizes it to engage magnetically the flutes successively as the shaft is manually rotated, stopping the rotary control at each rotational stop position. The switch also de-energizes the electromagnet so that the shaft may be continuously variable. A plurality of electromagnets can be positioned about a plate to vary the locations of the rotational stop positions. In a separate embodiment, a plurality of plates, each with an associated electromagnet, is mounted coaxially on the shaft.

Abstract: A signal coupling circuit suitable for use in a high-speed signal acquisition probe comprises separate high-frequency and low-frequency signal transmission paths from input to output. The low-frequency path includes a mechanism for variably shifting the DC voltage level at the circuit input to offset quiescent or average voltage levels of an input signal. Values of impedance elements for both the high-frequency and low-frequency transmission paths may be selected to provide predetermined input and output impedances without compromising signal fidelity or limiting signal bandwidth.

Abstract: A buffer amplifier suitable for use as an input amplifier for an oscilloscope comprises a hybrid FET-bipolar transistor source follower input stage and a complementary emitter follower output stage. Both the input and output stages include bootstraps to eliminate thermal transient response aberrations, to increase input impedance, and to maintain standing current in the output stage. Other attributes include a very short response time for high bandwidth operation, and high linearity.

Abstract: A feedbeside correction circuit for correcting errors in the frequency response of a wideband amplifier includes a network which models the physical distortion-producing mechanisms of the amplifier semiconductor pn junctions. An input signal is applied simultaneously to the amplifier and to the feedbeside circuit. The feedbeside circuit produces a correction signal which is applied to a summing node and subtracted from the amplifier signal so that the amplifier output is substantially error free. The circuit may be used both for single-ended and differential inputs.