KEITHLEY INSTRUMENTS, INC. Patent applications |
Patent application number | Title | Published |
20140354354 | NANOVOLT AMPLIFIER DESIGN - 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. | 12-04-2014 |
20140347158 | ISOLATION TRANSFORMER FOR USE IN ISOLATED DC-TO-DC SWITCHING POWER SUPPLY - 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. | 11-27-2014 |
20140306671 | HIGH PERFORMANCE CURRENT SOURCE POWER SUPPLY - 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. | 10-16-2014 |
20140285181 | DIGITAL VOLTMETER TOPOLOGY - 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. | 09-25-2014 |
20140218064 | SMU RF TRANSISTOR STABILITY ARRANGEMENT - 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. | 08-07-2014 |
20140167905 | HIGH VOLTAGE PROTECTION MODULE - A high voltage protection module can include a housing having two chambers and a wall separating the chambers. The wall can have a hole through which a conductive element can pass to electrically couple an input with an output. The conductive element can be configured to break or fuse with the hole responsive to a high voltage event at the input. | 06-19-2014 |
20140145729 | LOW FREQUENCY IMPEDANCE MEASUREMENT WITH SOURCE MEASURE UNITS - 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. | 05-29-2014 |
20140111188 | ACTIVE SHUNT AMMETER APPARATUS AND METHOD - 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. | 04-24-2014 |
20140111186 | IMPEDANCE SOURCE RANGING APPARATUS AND METHOD - An impedance sourcing circuit for a measurement device configured to measure a device under test (DUT) and method are disclosed. The impedance sourcing circuit includes a voltage/current source. An electrically controlled variable resistance having a control input is configured to adjust the variable resistance is coupled to the DUT. A loop gain controller is coupled to the control input of the electrically controlled variable resistance. The loop gain controller is configured to drive the control input of the electrically controlled variable resistance to adjust the variable resistance to generally match the impedance of the DUT. The impedance sourcing circuit may also include a voltage detector configured to detect a voltage across the DUT and a voltage reference. The loop gain controller may be configured to drive the control input of the electrically controlled variable resistance based on the voltage detected across the DUT and the voltage reference. | 04-24-2014 |
20140015612 | POWER ENVELOPE CONTROLLER AND METHOD - 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. | 01-16-2014 |
20130285629 | Dynamic Current Limit Apparatus and Method - A dynamic current limiter circuit is disclosed. The dynamic current limiter includes an input node an output node. The dynamic current limiter also includes a current control valve coupled between the input and output nodes, the current control valve being configured to limit current flow between the input and output nodes based on a control input. The dynamic current limiter also includes a current change detector coupled between the input and output nodes, the current change detector being configured to detect a change in current through the input and output nodes and generate a control signal configured to drive the control input. The current control valve is configured to limit current flow between the input and output nodes in response to the current control signal. | 10-31-2013 |
20130265110 | HIGH GAIN, HIGH VOLTAGE POWER AMPLIFIER - 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. | 10-10-2013 |
20130113511 | DC-AC PROBE CARD TOPOLOGY - 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. | 05-09-2013 |
20090273338 | ACTIVE AUTORANGING CURRENT SENSING CIRCUIT - A range-changing circuit for a measurement device having a desirable range includes an array of graduated impedances. And amplifier supplies an electrical voltage to at least one of the impedances of the array. A voltage sensing and limiting switch is provided in a feedback path of the amplifier. The switch limits said electrical voltage supplied to said at least one of the impedances in response to a sensed voltage that is sensed by the switch. An electrical voltage in the desirable range is developed across a different one of the impedances of the array based on an operation of the switch. | 11-05-2009 |
20090201822 | SWITCH MATRIX - A switch matrix for selectively connecting at least one of N signal inputs to at least one of M signal outputs, N and M being integers greater than two, includes a cluster of N input switches arranged about each of the M signal outputs resulting in at least M clusters of N input switches, each input switch having a switch input and a switch output, the switch outputs being connected to respective signal outputs, the clusters and the input switches in the clusters being arranged to permit adjacent switch inputs of adjacent clusters to be connected to form input switch nodes; and a steering switch for each of the signal inputs. The steering switch selectably connects a signal input to an input switch node, wherein the combination of the steering switches and the input switches are operable to connect a desired signal input to a desired signal output. | 08-13-2009 |
20090195261 | IMPEDANCE MEASURING INSTRUMENT - 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. | 08-06-2009 |
20090048800 | TEST INSTRUMENT NETWORK - A test instrument network for testing a plurality of DUTs includes a plurality of communicating script processors, the script processors being adapted to execute computer code; and a plurality of measurement resources controllable by the script processors in response to executed computer code, the measurement resources being adapted to test the DUTs. Each script processor and measurement resource may be arbitrarily assigned by the controller to one of at least two groups, only one script processor being assigned to be a master script processor, any other script processor being a slave script processor and any group not including the master script processor being a remote group. The master script processor is exclusively authorized to initiate code execution on any script processor in a remote group. Any slave script processor is only able to initiate operation of measurement resources in it own group. When a particular script processor is executing computer code, the master script processor may not initiate execution of computer code on a member script processor in the group of the particular script processor and may not initiate operation of a member measurement resource in the group of the particular script processor. | 02-19-2009 |
20080303535 | MULTI-PIN CV MEASUREMENT - A method for measuring electrical parameters of a DUT having at least three terminals includes applying a first AC voltage to a first terminal; separately driving a second and a third terminal each to a virtual second AC voltage, each virtual voltage requiring a respective current; and measuring an electrical parameter of the DUT based on the first AC voltage and the second and third terminals each being at the virtual second AC voltage. | 12-11-2008 |