Abstract: Two enhancement mode MOSFETs in series are used to provide a solid-state switch. The MOSFETs are turned on by a photovoltaic array. Resistors in series with the MOSFETs serve to provide a control voltage to current-limit the circuit. An additional photovoltaic array is used to supply drain to gate bias when the switch is off to minimize device capacitance. The circuits can be cascaded to raise the voltage-handling limits.

Abstract: A range selecting impedance is switched into or out of a parallel range-selecting network by connecting the impedance across the network through an n-channel and a p-channel FET connected in parallel output configuration. The n-channel FET does the switching if the drains are negative with respect to the sources. The p-channel FET does the switching if the drains are positive with respect to the sources. Each FET is controlled by a gate drive whose output waveform is varied to select the rate at which the FETs switch. In cases of several different switched range impedances, the FETs are used to switch the smallest impedance into the network, another range impedance is selected, and then the FETs used to switch the smallest impedance out of the network. In this way, fast glitch-free range switching is achieved.

Abstract: The frequency range and accuracy of a commercially available RMS converter is improved by providing an improved rectifier ahead of the converter's internal rectifier. The improved rectifier switches between the input signal and an inverted version of the input signal in response to a high speed comparator. The improved rectifier can also incorporate range selecting circuitry.

Abstract: An apparatus capable of acting as a current-limited voltage source or a voltage-limited current source is disclosed. The output of the apparatus is provided by a differential amplifier. The current and voltage outputs are compared to positive and negative current and voltage limits. Depending on whether the apparatus is in the voltage mode or the current mode, the inverting input of the differential amplifier is clamped to the appropriate voltage or current comparison signal, respectively, to provide an error signal to the differential amplifier. This clamping is current limited so that if the output current limits are exceeded while in the voltage source mode, a clamp to one of the current comparison signals occurs and dominates the voltage clamp. Similarly, if the output voltage limits are exceeded while in the current source mode, a clamp to one of the voltage comparison signals occurs and dominates the current clamp.

Abstract: Apparatus is provided for use in detecting the input voltage applied to a radiation source operating at an unknown voltage within a given voltage range. The apparatus includes a set of radiation absorbing filters including a first filter which includes a first chemical element and a second filter which includes a second chemical element. These elements are chosen so that the filters exhibit different radiation absorption characteristics within the given voltage range. The filters are adapted to be positioned so that the first and second filters are irradiated by the radiation source with the radiation impinging upon a surface of each filter and partially absorbed thereby as it passes therethrough so as to exit therefrom as attenuated radiation. A detector receives the attenuated radiation passed by the first and second filters and provides first and second signals having magnitudes which vary with the attenuated radiation respectively passed by the first and second filters.

Abstract: Apparatus is provided for use in detecting the peak voltage applied to a radiation source operating at an unknown input voltage. The apparatus includes a set of radiation absorbing filters including a first filter which includes a first element that exhibits a known K-absorption edge and a second filter constructed of a second element so that the filters exhibit essentially the same radiation absorption characteristics below the K-absorption edge of the first filter. The filters are adapted to be positioned so as to be irradiated by the radiation source so that the radiation impinges upon a surface of each filter and is partially absorbed as it passes therethrough so as to exit therefrom as attenuated radiation. A detector, such as X-ray film or a pair of photodiodes, is positioned for receiving the attenuated radiation passed by the first and second filters and provides an output indication when the radiation passed by the filters is differently attenuated.

Abstract: The JFET transistor differential amplifier herein serves as an input stage, as for an electrometer operational amplifier, and exhibits high input impedance and low leakage current. This is achieved by biasing the JFET transistors so as to operate in the ohmic region rather than the saturation region of their characteristic drain current-gate to source voltage curve.

Abstract: Electronic protective circuitry for protecting an electrical circuit, such as a constant current source circuit, from damage due to an overvoltage applied to the circuit. The protective circuit employs circuitry for limiting the magnitude of the voltage across a first portion of the circuit, such as an amplifier output circuit, so that the voltage thereacross is limited to a given maximum voltage level. A current limiter is connected in series between the first portion and second portion for limiting the magnitude of current flowing through the circuitry to a given maximum current level. Essentially all of the overvoltage is applied across the current limiter. The protective circuit is particularly applicable for protecting an amplifier from damage due to an overvoltage applied to its output circuit, as well as for protecting a resistor connected in series with the output circuit of the amplifier.