Abstract: A method for measuring the impedance of a DUT having a capacitance of less than 1 pF includes applying a voltage or current signal to the DUT, the voltage or current signal including an AC component having a non-zero frequency of less than 1 kHz; monitoring a current or voltage signal, respectively, through the DUT in response to the voltage or current signal; digitizing the voltage signal and the current signal synchronously; and calculating the impedance from the digitized voltage and current signals.

Abstract: A switch protection circuit includes a discharging circuit and, optionally, a clamping circuit. The discharge circuit operates prior to the switch completing the switching action to discharge capacitance from a signal line of a cable connected to a device under test to a ground voltage. When not discharging, the discharge circuit presents low leakage to a measurement circuit so as not to interfere with such measurement. If present, the clamping circuit clamps a signal line of the cable to a guard structure of the cable so that the discharge circuit can couple both the signal line and the guard structure to ground. The protection circuit operates without significantly worsening low current performance of the measurement instrument.

Abstract: A circuit can include operational amplifier having a first input, a second input, and an output, first and second resistors in series between the output of the op-amp and a ground, and multiple switches configurable to toggle the circuit between a positive phase and a negative phase.

Abstract: A method for compensating for a dielectric absorption effect in a measurement configuration during measurements by an instrument having measurement terminals includes providing a feedback loop in the instrument, the loop having a gain adjustment and a simulation impedance and being adapted to provide a signal counter to the dielectric absorption at the measurement terminals; applying a transient calibration signal to the test terminals for at least two values of the gain adjustment; measuring a response to the calibration signal for each of the at least two values; and determining an operating value of the gain adjustment based on the measured responses. The operating value is used for subsequent measurements by the instrument, the simulation impedance modeling the dielectric absorption characteristics of the measurement configuration.

Abstract: An isolated DC-to-DC switching power supply includes an isolation transformer having a magnetic core, a first winding around the magnetic core, a first winding-shield around the magnetic core, a second winding-shield within the first winding-shield, and a second winding within the second winding-shield. There is no direct coupling between the first winding and the second winding since the second winding is enclosed within the second winding-shield and the second winding-shield is enclosed within the first winding-shield.

Abstract: A measurement instrument for measuring the impedance of a device under test (DUT) includes a first source of either a voltage or a current and a second source of either a voltage or a current, wherein the first source is connectable in a first feedback relationship with the DUT and the second source is connectable in a second feedback relationship with both the DUT and the first source. The first and second sources are operated respectively as a current source responsive to the current through the DUT and a voltage source responsive to the voltage across the DUT or operated respectively as a voltage source responsive to the voltage across the DUT and a current source responsive to the current through the DUT. The second feedback relationship has a narrower bandwidth than the first feedback relationship. The resulting voltage across the DUT and the current through the DUT establish the measured impedance of the DUT.

Abstract: A system can include a device under test (DUT) having a DUT voltage, a cable connected to the DUT, the cable having a cable inductance, and a power supply configured as a current source to provide a wide bandwidth voltage source to the DUT, wherein the DUT voltage is independent of the cable inductance.

Abstract: A system may include two input terminals, e.g., HI and LO, and a floating circuit that is physically separate from the input terminals and includes a gain amplifier. The floating circuit can be surrounded by a conductive enclosure that is electrically connected to the second input terminal. The floating circuit can further switch between input signals received from the first and second input terminals to the gain amplifier and the floating circuit ground.

Abstract: A method for verifying the adjustment for the purpose of calibration of an impedance meter having at least a first and a second measurement range includes measuring within the first range a first measured value of a test impedance; measuring within the second range a second measured value of the test impedance; and comparing the first and second measured values to verify the calibration of the impedance meter.

Abstract: An RF testing method and system by which a DC measurement pathway can also act like a properly terminated RF pathway. Achieving this requires that the output HI, LO, and Sense HI conductors are terminated in a frequency selective manner such that the terminations do not affect the SMU DC measurements. Once all SMU input/output impedances are controlled, as well as properly terminated to eliminate reflections, the high-speed devices will no longer oscillate during device testing, so long as the instruments maintain a high isolation from instrument-to-instrument (separate instruments are used on the gate and drain, or on the input and output of the device). The output of HI, LO and Sense HI conductors are coupled to various nodes of the DUT via three triaxial cables, the outer shieldings of which are coupled to each other and to an SMU ground.

Abstract: A power envelope controller configured for use with an amplification stage and method are disclosed. The power envelope controller includes voltage feedback input circuitry configured to receive a voltage feedback signal representing an internal voltage drop across the amplification stage and current feedback input circuitry configured to receive a current feedback signal representing an output current of the amplification stage. An analog multiplier is configured to generate an internal power dissipation signal representing the internal power dissipation of the amplification stage based on the voltage and current feedback signals. A comparator circuit is configured to compare the internal power dissipation signal to a power threshold and generate a power control error signal when the internal power dissipation of the amplification stage exceeds the threshold.

Abstract: A DC-AC probe card for testing a DUT includes: a plurality of probe needles, each probe needle having a distal end for contacting said DUT; and a plurality of connection pathways operable to connect test instrumentation to the probe needles, wherein each connection pathway provides both a desired characteristic impedance for AC measurements and a guarded pathway for DC measurements between respective test instrument connections and probe needles.

Abstract: An opto-isolated amplifier and method are disclosed. The amplifier includes an input node configured to receive an input to be amplified. A pair of opto-isolators are coupled between an input node and an output node. The opto-isolators are configured to create gain between the input node and the output node. An amplification stage is coupled to the opto-isolators. The amplification stage includes an input coupled to the output node and an output configured to generate an amplified output. The opto-isolator outputs may be configured to generate a difference current. The input of the amplification stage may have a high impedance compared to an impedance at the output node, the difference current being directed at the high input impedance input of the amplification stage to generate a gained voltage.

Abstract: An active shunt ammeter for measuring current flowing through a device under test (DUT) and method are disclosed. The active shunt ammeter includes an input configured to receive an input signal having a frequency within a frequency band and representing the current flowing through the DUT. An output is configured to generate an output voltage representing the current flowing through the DUT. The active shunt ammeter also includes a gain circuit having an amplifier with a gain characteristic that varies respect to frequency within the frequency band and a feedback element having an impedance coupled from an output of the gain circuit to a negative input of the gain circuit, the feedback element impedance being configured to change with frequency to correlate with the amplifier gain characteristic such that the feedback element impedance divided by the amplifier gain over the frequency band has minimal frequency dependency.

Abstract: A multiplexor includes an output having a characteristic impedance; a first input having a characteristic impedance equal to the output characteristic impedance; a second input; a first switch path including a first switch operable to connect/disconnect the first input center conductor and the output center conductor; a first input conductive path adjacent to the first switch path and being operable to provide the output characteristic impedance; a second switch path including a second switch operable to connect/disconnect the second input first signal conductor and the output center conductor; and a third switch path including a third switch operable to connect/disconnect the second input second signal conductor and the output intermediate conductor, the third switch path being operable to guard the second switch path when the third switch path is provided with a guard voltage.

Abstract: An apparatus for testing a DUT includes a pulsed signal source; a hard current-limiter adapted to be operated in series relationship between the pulsed signal source and the DUT; and a voltage sensor adapted to sense a voltage across the DUT in response to the pulsed signal source.

Abstract: Provided is printed circuit board for minimizing dielectric losses experienced by a low-current portion of an electric circuit. The printed circuit board includes a first substrate supporting an electrically-conductive material patterned to form a conductive pathway between electric circuit components, and a surface-mount guard pad provided on a substantially-planar exposed surface of the first substrate and covering at least an area of the exposed surface including a footprint of the low-current portion on the first substrate. A second substrate is also provided with one or more electrically conductive pads that are surface mounted to the guard pad to couple the second substrate to the guard pad. The second substrate also supports a signal trace included in the low-current region for conducting a low-current signal.

Abstract: Provided is a method and system for distributing a test recipe to a tester for conducting a test to determine if a device under test operates as designed. The method includes storing an active test recipe in an active memory in local communication with the tester, and initiating the test of the device under test to be performed by the tester according to a parameter included in the active test recipe stored in the active memory. A second parameter included in a second test recipe is received by the tester while conducting the test of the device under test according to the parameter included in the active test recipe. The method further includes storing the second parameter in a buffer memory in local communication with the active memory, and initiating a transfer of the second parameter from the buffer memory to the active memory.

Abstract: A system for making high frequency measurements on a DUT includes a high frequency measurement instrument; a plurality of DUT probes; a first coaxial cable having a center conductor and a coaxial conductor for connection between the instrument and a first DUT probe; and a second coaxial cable having a center conductor and a coaxial conductor for connection between the instrument and a second DUT probe, at least one of the first and second cables being selectively shortable between the respective center conductor and coaxial conductor at a location near the respective DUT probe.

Abstract: A method for operating a measurement system having an interconnect between the measurement system and a device under test (DUT), the interconnect exhibiting voltage drops during measurements of the DUT, includes applying a test signal to the DUT through the interconnect, the test signal having a system value at the measurement system; measuring a resulting DUT value at the DUT; adjusting the system value according to the resulting DUT value to produce successive desired DUT values at the DUT; and using the successive DUT values to measure an electrical characteristic of the DUT.