A Measurement Example
This example provides a general overview for performing a measurement. Using the supplied model bjt_npn.mdl, the example measures the forward early voltage of an npn bipolar device using the SMUs of the HP 4141 DC Analyzer.
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Note
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Before starting the measurement example, follow the procedures in Opening a Model File to open the model bjt_npn.mdl.
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Hardware Setup
The HP 4141 contains four SMUs (Source/Measurement Units), each capable of sourcing and measuring voltage and current. For each SMU, a single triaxial cable carries the input signal to the device and the output signal from the device.
To connect the hardware:
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Connect a cable from each of the four connectors (marked SMU1 - SMU4) on the back of the HP 4141 to each of the four connectors (marked SMU1 - SMU4) on the back of the HP 16058 Test Fixture. |
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Insert the bipolar npn test device into the HP 16058 Test Fixture and make the appropriate SMU to device lead connections. |
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Connect an GPIB cable from the GPIB connector on the back of the HP 4141 to the GPIB bus connector on the computer. |
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Make sure the GPIB address is set to a value that does not conflict with other GPIB addresses on the bus. |
To setup the hardware:
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In the IC-CAP/Main window, click Hardware Setup. |
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A dialog box opens. In the Name field, type the name of the interface, hpib. |
- IC-CAP finds the device and adds HP 4141 to the Active Instruments list.
When the HP 4141 is added to the active instrument list, the corresponding units are added to the Unit Table. The Unit Table contains an entry for each active unit.
To view unit names:
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Select Configure. A dialog box opens, displaying the Unit Table and Instrument Address. |
- For this example, the units of the HP 4141 are: HP4141.7.23.SMU1, HP4141.7.23.SMU2, HP4141.7.23.SMU3, HP4141.7.23.SMU4, HP4141.7.23.VS1, HP4141.7.23.VS2, HP4141.7.23.VM1, and HP4141.7.23.VM2.
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No changes are made. Choose Cancel. |
Assigning Units to a Setup
The next step explains how to use these unit names in a setup to specify a particular measurement. The bjt_npn model already includes setup specifications for the inputs vb, vc, ve, and vs, and the output ic. The assigned unit names are entered in the Unit field of the Input and Output tables. By specifying the unit names, you assign the HP 4141 to the setup fearly.
To specify unit names in a setup:
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In the Model window, select DUTs-Setups. |
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Select the DUT dc and the setup fearly. |
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In the Measure/Simulate folder, select the Input table vc. |
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In the dialog box, edit the Unit field by entering SMU1. |
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Repeat steps 3 through 6, assigning SMU2 to the Unit field of the Input vb, SMU3 to the Unit field of the Input ve, and SMU4 to the Unit field of the Input vs. To monitor the output, assign SMU1 to the Unit field of Output ic. |
Specifying Instrument Options
The HP 4141 has four instrument options that may be set before taking a measurement.
To view instrument options:
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Select Instrument Options. |
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For this example, the default values of these options are used. |
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Since the option Use User Sweep is set to No, the main sweep Input vc (Sweep Order = 1) is swept from 0.000 to 5.000 volts in 21 steps using an internal instrument sweep. |
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Note
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When Use User Sweep is set to Yes, the measurement is taken from 0.000 to 5.000 volts in 21 steps, with each voltage being set separately or point-by-point. A measurement taken with a user sweep is slower than the same measurement taken with an internal instrument sweep. However, the advantage for using a user sweep is increased flexibility in the types of measurements that can be taken.
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The Hold Time option is set to 0.000. This means that the instrument waits 0.000 seconds before starting the main sweep. |
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The Delay Time option is set to 0.000. This means that the instrument waits 0.000 seconds before the measurement is taken at each step in the sweep. |
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The Integration Time is set to S. This means that the integration time of the HP 4141 is short. |
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Since no changes are made, choose Cancel. |
To take a measurement:
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Select Measure/Simulate |
- The system status line in the IC-CAP/Status window displays:
- Measure in progress...
- When the measurement is done, the status line displays:
- IC-CAP Ready
- The IC-CAP measurement is complete.
To view results:
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Click Display Plot. A plot of the measured data displays in a separate window. |
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