NI ELVIS - Three-Wire Current-Voltage Analyzer SFP Collected and Edited by: Ahmed Haytham The NI ELVIS Three-Wire Current-Voltage Analyzer SFP is a top-level, stand-alone instrument that is a basic 3-wire current versus voltage curve tracer for NPN BJT transistors. The instrument utilizes the NI ELVIS hardware, the DAQ AO and the DAQ AI. It is capable of displaying signals within 0–10 V for the collector voltage and 0– 10 mA for the collector current. You must set the base current steps and specify the range of the collector voltage sweep. Connect the device under test in the following manner: 3-WIRE Collector connection CURRENT HI Base connection CURRENT LO Emitter connection Notes The AO resolution of a 12-bit DAQ device in combination with the NI ELVIS hardware requires that the number of allowable base current steps are limited. CURRENT LO is a virtual ground input and should not be subjected to a DC offset. This section explains the NI ELVIS - Three-Wire Current-Voltage Analyzer SFP and describes how to measure a signal with the SFP. To launch the software instruments, select Start» Programs» National Instruments» NI ELVIS 2.0» NI ELVIS to load the Instrument Launcher, then click the button for the desired instrument on the NI ELVIS Instrument Launcher. Display Window Display Window—Contains the collector current-voltage plot for the device under test as well as cursors. You can move the cursor horizontally by clicking on it and dragging it along the voltage axis. The signal is plotted current versus voltage. The Display Window also includes the following groups of indicators. NPN Connection Indicators— Voltage (V)—Displays the measured collector voltage during a voltage sweep or cursor movement. The units for this measurement are volts. When cursors are disabled, the values displayed during a sweep correspond to the first base current curve. Current (A)—Displays the measured collector current for the applied test voltage during a voltage sweep or cursor movement. The units for this measurement are amps. When cursors are disabled, the values displayed during a sweep correspond to the first base current curve Base Current Settings Base Current Start—Specifies the start value of the base current curves. The default value is 15 µA. Base current is generated using the DAQ AO channel DAC0 and series resistance. Number of Curves—Specifies the number of base current curves to generate. The default value is 3. Base Increment—Specifies the spacing between each base current curve. Increment values are limited to 15 µA steps for hardware compatibility between 12- and 16-bit DAQ devices. The default value is 15 µA. Collector Voltage Settings Start—Specifies the voltage at which to start the collector voltage sweep. The default value is 0 V. Stop—Specifies the voltage at which to stop the collector voltage sweep. The default value is 2 V. Increment—Specifies the voltage spacing between measurements during the voltage sweep. The default value is 0.1 V. Collector Current Limit—Specifies the maximum allowed collector current allowed during the voltage sweep. If the measured current exceeds this limit, the sweep stops. The default value is 10 mA. Display Controls Autoscale—Determines if the Three-Wire Display autoscales. The default value is ON. If autoscaling is not on, the graph ranges are 0–10 mA and 0–10 V. Mapping o Voltage—Selects whether the X-axis (Collector Voltage) on the Three- Wire Display is displayed in logarithmic or linear scale. The default value is Linear. o Current—Selects whether the Y-axis (Collector Current) on the Three- Wire Display is displayed in logarithmic or linear scale. The default value is Linear. Cursor—Turns the display of the cursor on and off. The cursor is locked a display plot so the up and down arrows on the control do not affect cursor position. The default value is OFF. Ib Curve—Selects the base collector curve to which the cursor is attached. This control is only available when cursors are enabled. The control entries correspond to base current values selected in the base current settings. The default value is the first curve. Position—Moves the cursor to the left or right, one point at a time, for precise cursor positioning. Run Button—Starts or stops the voltage sweep with the parameters specified by the Settings controls. The default value is OFF. Log—Generates a comma-delimited text file with the voltage and current data of the last voltage sweep. Logging is available when no acquisitions are occurring. A timestamp appears at the beginning of the file. If an existing file is selected, the new data is appended at the end of the file. Caution By connecting different signals to both the DMM terminals on the prototyping board and the DMM connectors on the control panel, you are shorting them together, potentially damaging the circuit on the prototyping board. Complete the following steps to start measuring signals with the NI ELVIS - Three-Wire Current-Voltage Analyzer SFP: Note Currently, this instrument only supports NPN BJT transistors. 1. Connect the three-terminal device you want to analyze in the following manner: NPN BJT transistor: 3-WIRE collector connection CURRENT HI base connection CURRENT LO emitter connection 2. Launch the NI ELVIS - Three-Wire Current-Voltage Curve Analyzer SFP from the NI ELVIS Instrument Launcher. Refer to Launching the SFP Instruments for more information. 3. Adjust the Collector Current Limit control as desired. 4. Select the desired base current settings. 5. Select the starting and ending collector voltages from the Start and Stop controls, and click Run.