High Voltage Transistor Tester with the Analog Discovery Pro 5250

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 to the maximum output current of the supplies, a $R=\frac{V}{I}=\frac{V_{+}-V_{-}}{I}=\frac{25V+25V}{0.5A}=100Ω$ resistor is needed in series with the transistor.

The maximum output current of the ADP5250 on the +25V and -25V supplies 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 $P_{R}=I_{Rmax}*V_{Rmax}=0.5A*50V=25W$ which is higher then the rated power of the 10W ceramic resistors. To protect the circuit, two pieces of 51Ω resistors will be used in series, so the voltage is divided equally between them, the dissipated power being only half, which is 12.5W. This is still above 10W so the maximum voltage should also be reduced. If the maximum voltage drop is only 40V, the dissipated power by the resistors will be $P_{51R}=\frac{I_{Rmax}*V_{Rmax}}{2}=\frac{0.5*40V}{2}=10W$

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.

Import the necessary packages into your script and define the measurement parameters.

from WF_SDK import device, supplies, wavegen, dmm # import instruments
import time                     # needed for delays
import matplotlib.pyplot as plt # needed for plotting
 
"""-----------------------------------------------------------------------"""
 
# parameters
Vd_resolution = 500 # drain voltage resolution in mV
Vd_limit = 40       # maximum drain voltage in V
Vg_resolution = 2   # gate voltage resolution in V
Vg_limit = 12       # maximum gate voltage in V
delay_time = 0.1    # time between samples in seconds
transistor = "ZVN3310A"

Connect to the device, initialize the digital multimeter and generate the lists of voltages which will be generated in the following. Also create empty lists for the results.

# connect to the device
device_handle, device_name = device.open("Analog Discovery Pro 5250")
 
# check for connection errors
device.check_error(device_handle)
 
"""-----------------------------------"""
 
# initialize the scope
dmm.open(device_handle)
 
# generate voltages list
Vd = range(0, int((Vd_limit  * 1000) + Vd_resolution), int(Vd_resolution))
Vg = range(Vg_resolution * 1000, int((Vg_limit + Vg_resolution) * 1000), int(Vg_resolution * 1000))
 
# convert from mV to V
Vd = [element / 1000 for element in Vd]
Vg = [element / 1000 for element in Vg]
 
# create empty lists for the results
Vds = [[] for _ in Vg]
Id = [[] for _ in Vg]

Step through the list of gate-source voltages. Output every voltage on the waveform generator.

For every gate-source voltage, step through the list of drain voltages, outputting each on the +25V supply. After the voltage change is commanded, wait a bit for the supply voltage to settle, then use the digital multimeter to measure the drain-source voltage and the drain current. Don't forget to invert the voltage.

try:
    index = 0
    for gate_voltage in Vg:
        # set the gate voltage
        print("Gate-Source Voltage: " + str(gate_voltage) + "V")
        wavegen.generate(device_handle, 1, wavegen.function.dc, gate_voltage)
        for drain_voltage in Vd:
            print("\tDrain voltage: " + str(drain_voltage) + "V")
            # set the drain voltage
            if drain_voltage > 25:
                supplies.switch_25V(device_handle, True, True, drain_voltage - 25, -25)
            else:
                supplies.switch_25V(device_handle, True, True, 0, drain_voltage * (-1))
 
            # delay
            time.sleep(delay_time)
 
            # measure the drain-source voltage
            Vds[index].append((-1) * dmm.measure(device_handle, "voltage"))
 
            # measure the drain current
            Id[index].append(dmm.measure(device_handle, "high current"))
        index += 1
except:
    pass
 
print("Done")

When the measurement is finished, close every instrument and disconnect from the device.

# reset the scope
dmm.close(device_handle)
 
# reset the wavegen
wavegen.close(device_handle)
 
# reset the power suplpies
supplies.switch_25V(device_handle, False, False, 0, 0)
supplies.close(device_handle)
 
# close the connection
device.close(device_handle)

Finally, plot the results.

# plot results
for index in range(len(Vg)):
    try:
        plt.plot(Vds[index], Id[index], label=(r"$V_{GS}$" + "=" + str(Vg[index]) + "V"))
    except:
        pass
plt.xlabel(r"$V_{DS}$" + "[V]")
plt.ylabel(r"$I_{D}$" + "[A]")
plt.legend()
plt.title(transistor)
plt.show()

Turn on the ADP5250 and start the script. Wait for it to finish. You can save the plotted results by clicking on the respective button. Compare your results to the one presented in the datasheet of the transistor.