公开(公告)号：US20170146575A1

公开(公告)日：2017-05-25

申请号：US15359462

申请日：2016-11-22

Applicant: NATIONAL INSTRUMENTS CORPORATION

Inventor： Pablo E. Limon-Garcia-Viesca ,  Christopher G. Regier

IPC: G01R19/32 ,  G01R19/00 ,  G01R15/14

CPC classification number: G01R19/32 ,  G01R15/146 ,  G01R19/0092

Abstract: A source-measure unit (SMU) may be implemented with digital control loops and circuitry to digitally compensate for the impact of input bias current on current measurements. One or more buffers having well-defined characteristics with respect to certain parameters which may affect the current measurements may be used in the output signal path of the SMU where a shunt voltage developed across a current sense element is measured. For example, the buffers may conduct/develop respective input bias currents that change perceptibly and predictably with temperature. By measuring the temperature and adjusting a control voltage—which is used to develop the shunt voltage—according to the temperature measurements, the impact of the input bias current[s] on the current measurement[s] may be reduced to negligible levels and/or may be eliminated. The control voltage may be adjusted by adjusting a voltage feedback value representative of the measured shunt voltage, and/or by adjusting a current setpoint used for generating the control voltage.

公开(公告)号：US10338110B2

公开(公告)日：2019-07-02

申请号：US15359462

申请日：2016-11-22

Applicant: NATIONAL INSTRUMENTS CORPORATION

Inventor： Pablo E. Limon-Garcia-Viesca ,  Christopher G. Regier

IPC: G01R19/32 ,  G01R15/14 ,  G01R19/00

Abstract: A source-measure unit (SMU) may be implemented with digital control loops and circuitry to digitally compensate for the impact of input bias current on current measurements. One or more buffers having well-defined characteristics with respect to certain parameters which may affect the current measurements may be used in the output signal path of the SMU where a shunt voltage developed across a current sense element is measured. For example, the buffers may conduct/develop respective input bias currents that change perceptibly and predictably with temperature. By measuring the temperature and adjusting a control voltage—which is used to develop the shunt voltage—according to the temperature measurements, the impact of the input bias current[s] on the current measurement[s] may be reduced to negligible levels and/or may be eliminated. The control voltage may be adjusted by adjusting a voltage feedback value representative of the measured shunt voltage, and/or by adjusting a current setpoint used for generating the control voltage.

公开(公告)号：US20180267096A1

公开(公告)日：2018-09-20

申请号：US15922051

申请日：2018-03-15

Applicant: NATIONAL INSTRUMENTS CORPORATION

Inventor： Blake A. Lindell ,  Pablo E. Limon-Garcia-Viesca

IPC: G01R31/28 ,  H03M1/10 ,  G01R1/30 ,  G01R27/26

CPC classification number: G01R31/2837 ,  G01R1/30 ,  G01R19/0007 ,  G01R23/16 ,  G01R27/26 ,  H03M1/1071

Abstract: A method and apparatus for simultaneously testing a component at multiple frequencies is disclosed. A digital processing circuit may generate a digital representation of a signal having a plurality of sine waves, each having a unique frequency. The digital representation may be converted into an analog signal, and applied to a device under test (DUT). A first analog-to-digital converter (ADC) may be coupled to measure voltages across the DUT, while a second ADC may be coupled to measure currents through the DUT. Voltage and current signals received by the first and second ADCs, respectively, may be converted into first and second digital values. Voltage and current values at each unique frequency are determined from the first and second digital values. Using the voltage and current values for each unique frequency, a frequency response of the component (e.g., an impedance) over a range of frequencies may be determined.