Abstract: A test and measurement device, including a first input structured to receive a first voltage from a first conductor of a first triaxial cable, a second input structured to receive a second voltage from a second conductor of the first triaxial cable or a second triaxial cable, circuitry configured to change modes based on the first voltage and the second voltage; and an output structured to output a signal.

Abstract: A current source has at least one gain component having a constant gain at frequencies below a frequency point, and having a gain inversely proportional to frequency at frequencies above the frequency point, the gain component having an input and an output, a source resistor connected in series with the output of the gain component, the gain component to regulate a voltage across the source resistor to be a source voltage, such that the gain of the gain component limits regulation by the gain component of the source voltage and an output voltage across a load between a high terminal and a low terminal, and a feedback component to receive at least a portion of the output voltage, the feedback component connected to the input of the gain component, the feedback component configured to reduce the gain of the gain component available to regulate the source voltage across the source resistor.

Abstract: A digitizing circuit includes a port connectable to a device under test (DUT), an integrating analog-to-digital converter (ADC), a high-speed ADC, one or more processors to apply a digital filter to output samples of the high-speed ADC to produce filtered samples, find differences between the filtered samples and samples from the integrating ADC to produce error values, and add the error values to the output samples of the high-speed ADC. A method of producing a digital signal includes receiving an input analog signal at an integrating analog-to-digital converter (ADC) and a high-speed ADC, applying a digital filter to output samples of the high-speed ADC to produce filtered samples, the digital filter matched to timing and filtering of the integrating ADC, finding differences between the filtered samples to output samples of the integrating ADC to produce error values, and adding the error values to the output samples of the high-speed ADC.

Abstract: A dual-stage source measure unit (SMU) has a user interface to allow a user to input one or more target values, at least two terminals to couple to a device under test (DUT), a current loop having a current digital control loop (DCL), a current digital-to-analog converter (DAC), a sense resistor, a current analog-to digital converter (ADC), and a common ADC, the current DCL to receive inputs from the current ADC, from the common ADC, and a target value for the output current, and to control a first output stage to produce the output current, and a voltage loop having a voltage DCL, a voltage DAC, a voltage ADC, and the common ADC, the voltage DCL to receive inputs from the voltage ADC, from the common ADC, and a target value for the output voltage, and to control a second output stage to produce the output voltage.

Abstract: A source measure unit has a voltage output stage to provide a voltage across first and second output terminals to connect to a load, and a current output stage to provide a voltage to a first sense resistor, the source measure unit to switchably employ both the voltage output stage and the current output stage for a first range of output current, to regulate a common point, and either output voltage or output current, or employ only one of either the voltage output stage or the current output stage to provide voltage to both the first and second output terminals and a second sense resistor for a second range of output current, and to regulate either output voltage or output current.

Abstract: A test and measurement instrument includes a current measurement device having an input to accept an electrical current for measurement, an output to pass an output current output from the current measurement device, a sense path through which the electrical current is measured, and an active bypass device to pass an amount of current from the input of the current measurement device to the output of the current measurement device without passing through the sense path. The active bypass device may be tuned to allow the current sense device to operate without bypass within a specific range of target current values. Some current measurement devices may include more than one active bypass circuits, each tuned for a different range of input current values.

Abstract: A switching power supply can include multiple power MOSFETs that receive an initial gate drive waveform comprising a fast slew rate region having a negative slope and a slow slew rate region also having a negative slope. The MOSFETs can turn off during the slow slew rate region of the initial gate drive waveform.

Abstract: A feedback ammeter, which may be included in a source measure unit or a digital multi-meter, for example, including an operational amplifier having an input and an output and a feedback path electrically coupled between the output and the input of the operational amplifier. The feedback path includes a first non-linear device to allow the measurement of decades of current. The ammeter also includes an amplifier electrically coupled to the input of the operational amplifier and the output of the operational amplifier, a second non-linear device electrically coupled to an output of the amplifier, and a resistor electrically coupled between the second capacitor and the input of the operational amplifier. A constant resistance input impedance is established using the second non-linear device that can adjust the circuit gain.

Abstract: A test and measurement device, including a first input structured to receive a first voltage from a first conductor of a first triaxial cable, a second input structured to receive a second voltage from a second conductor of the first triaxial cable or a second triaxial cable, circuitry configured to change modes based on the first voltage and the second voltage; and an output structured to output a signal.

Abstract: A current source has at least one gain component having a constant gain at frequencies below a frequency point, and having a gain inversely proportional to frequency at frequencies above the frequency point, the gain component having an input and an output, a source resistor connected in series with the output of the gain component, the gain component to regulate a voltage across the source resistor to be a source voltage, such that the gain of the gain component limits regulation by the gain component of the source voltage and an output voltage across a load between a high terminal and a low terminal, and a feedback component to receive at least a portion of the output voltage, the feedback component connected to the input of the gain component, the feedback component configured to reduce the gain of the gain component available to regulate the source voltage across the source resistor.

Abstract: A test and measurement device including a source configured to output a source signal, a source output configured to output the source signal to a connected cable, a guard drive circuit electrically coupled to the source and configured to receive the source signal and generated a guard drive signal, the guard drive circuit having a gain less than one, and a guard drive circuit output configured to output the guard drive signal to a connected guard.

Abstract: A nested ammeter for measuring the electrical current flowing through a device under test (DUT) can include an input configured to receive an input signal having a frequency within a frequency band and representing the electrical current flowing through the DUT. The nested ammeter can also include an output configured to generate an output voltage representing the electrical current flowing through the DUT. An active shunt can be used as the resistive feedback of the ammeter. A nested active shunt can be used as the resistive feedback element of the active shunt.

Abstract: A test and measurement instrument includes a current measurement device having an input to accept an electrical current for measurement, an output to pass an output current output from the current measurement device, a sense path through which the electrical current is measured, and an active bypass device to pass an amount of current from the input of the current measurement device to the output of the current measurement device without passing through the sense path. The active bypass device may be tuned to allow the current sense device to operate without bypass within a specific range of target current values. Some current measurement devices may include more than one active bypass circuits, each tuned for a different range of input current values.

Abstract: A test and measurement device including a source configured to output a source signal, a source output configured to output the source signal to a connected cable, a guard drive circuit electrically coupled to the source and configured to receive the source signal and generated a guard drive signal, the guard drive circuit having a gain less than one, and a guard drive circuit output configured to output the guard drive signal to a connected guard.

Abstract: A feedback ammeter, which may be included in a source measure unit or a digital multi-meter, for example, including an operational amplifier having an input and an output and a feedback path electrically coupled between the output and the input of the operational amplifier. The feedback path includes a first non-linear device to allow the measurement of decades of current. The ammeter also includes an amplifier electrically coupled to the input of the operational amplifier and the output of the operational amplifier, a second non-linear device electrically coupled to an output of the amplifier, and a resistor electrically coupled between the second capacitor and the input of the operational amplifier. A constant resistance input impedance is established using the second non-linear device that can adjust the circuit gain.

Abstract: Embodiments of the present invention provide an improved two-cable connection system for connecting electrical test instrumentation to a device under test (DUT). In one embodiment, a single pair of equal-length triaxial cables each has a desired characteristic impedance. Each cable has a center connecter, intermediate conductor, and outer conductor. The proximal end of each cable is connected to the test instrumentation, and the distal ends are located at the DUT. At the distal end, the center conductors are connected to the DUT, the intermediate conductors are allowed to float, and the outer conductors are connected to each other. The proximal end of each cable is connected to the device using an appropriate connection for the test that will be performed. This allows the test instrumentation to perform different types of tests without changing connections to the DUT.

Abstract: A nested ammeter for measuring the electrical current flowing through a device under test (DUT) can include an input configured to receive an input signal having a frequency within a frequency band and representing the electrical current flowing through the DUT. The nested ammeter can also include an output configured to generate an output voltage representing the electrical current flowing through the DUT. An active shunt can be used as the resistive feedback of the ammeter. A nested active shunt can be used as the resistive feedback element of the active shunt.

Abstract: Embodiments of the present invention provide improved techniques and devices for reducing transformer commutation distortion caused by large load currents. Traditional power supplies which have two or more phases typically commutate a transformer during the end of each phase. When the load current is large, energy stored in the transformer's leakage inductance can cause undesirable effects during commutation. Embodiments of the present invention reduce these effects by lowering the voltage across the primary side of the transformer prior to commutation. In one embodiment, a capacitor is added to the primary side of the transformer. A switch directs current through the capacitor prior to commutation, allowing the capacitor to absorb the transformer's leakage inductance energy and lower the primary side voltage. Other suitable components, such as resistors, diodes, transistors, or additional transformer windings, may also be used to reduce the primary-side voltage prior to commutation.

Abstract: A voltage clamp circuit which operates using a voltage controlled current source where the change of the polarity of the voltage controlled current source controls whether it is clamping or not. While clamping, the stability of the control loop uses the capacitance of the output to create and single pole roll-off of the loop gain and while not clamping, uses the capacitance of the circuit which sets the clamping voltage to produce the roll-off. The circuit operates in a linear fashion both while clamping and not clamping, which allows for a faster response when clamping is needed.

Abstract: Embodiments of the present invention provide improved techniques and devices for reducing transformer commutation distortion caused by large load currents. Traditional power supplies which have two or more phases typically commutate a transformer during the end of each phase. When the load current is large, energy stored in the transformer's leakage inductance can cause undesirable effects during commutation. Embodiments of the present invention reduce these effects by lowering the voltage across the primary side of the transformer prior to commutation. In one embodiment, a capacitor is added to the primary side of the transformer. A switch directs current through the capacitor prior to commutation, allowing the capacitor to absorb the transformer's leakage inductance energy and lower the primary side voltage. Other suitable components, such as resistors, diodes, transistors, or additional transformer windings, may also be used to reduce the primary-side voltage prior to commutation.