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High Voltage Transistor Tester with the Analog Discovery Pro 5250

While you can use the Transistor Tester Adapter to test small signal bipolar junction transistors (BJTs) and field-effect transistors (FETs) with the Analog Discovery 2, several mid- to high power devices are out of the range of these devices. In these cases, you can use the variable voltage supply and the digital multimeter on the ADP5250 to create your high voltage test bench and to plot the characteristic curves of power transistors.

Inventory

Hardware

Software

  • WaveForms SDK (installed with WaveForms)
  • Python
  • a text editor of your choice

Note: In this demo, the Python package created in the Getting Started with WaveForms SDK guide will be used. To write the Python script without using this package, check the WaveForms SDK Resource Center.

Connecting the Transistor to the ADP5250

In this test, the drain current versus the drain-source voltage of the selected MOSFET will be plotted for varying gate-source voltages. Connect the gate of the transistor to the waveform generator and the source to the ground.

To limit the maximum drain current, a 50Ω resistor is needed in series with the transistor. The maximum output current of the ADP5250 on the +25V supply is 500mA, so the maximum power dissipated by the resistor, in the case of an ideal switch instead of the MOSFET (with 0Ω resistance), would be $P_{R}={I_{R}}^{2}*R={(0.5A)}^{2}*50Ω=(0.25*50)W=12.5W$ which is higher then the rated power of the 10W ceramic resistors so two pieces of 100Ω resistors will be used in parallel (the current is divided equally between them, so the dissipated power will be only half, which is 6.25W, below 10W).

Connect the ampere meter of the DMM in series with the resistors. As the ampere meter and the voltmeter use the same reference, which is already connected to the drain, connect the positive lead of the voltmeter to the source of the MOSFET. The measured voltage will be inverted, but the results can be multiplied with -1 from software.

Use the high scale ampere meter on the DMM!

Writing the Script

Testing

Next Steps

For more guides on how to use your Digilent Test & Measurement Device, return to the device's Resource Center, linked from the Test and Measurement page of this wiki.

For information on the Transistor Tester Adapter, check out its Resource Center.

For technical support, please visit the Test and Measurement section of the Digilent Forum.