n-channel MOSFET

This page describes how to measure the characteristics of a n-channel MOSFET. Some basic information about the structure of MOSFETs can be found here: How does a MOSFET work? The following MOSFET was characterized: Datasheet IRF840A

In this experiments a Keithley 2600 Series Sourcemeter was used.

The Measurements were performed at ambient conditions and room temperature: T = (23,00,5)C

First the output characteristics were measured for different Gate Voltages, using the python code shown below. The MOSFET was connected the following way: SMUA und SMUB Low on Source, SMUA High on Gate and SMUB High on Drain.


nMOSFET_outputcurve.py

This script requires the Keithley 2600 Python library. Save this in your working directory.

As can be seen in the figure below, a higher Gate voltage results in a higher Source-Drain current. At low Source:Drain voltage a exponential growth can be observed, which flatten for higher voltages. This change marks the saturation region of the n-channel MOSFET.

Next the transfer characteristics were measured for different Drain-Source Voltages, using the python code shown below. To do so, the MOSFET was connected in the same way as before: SMUA und SMUB Low on Source, SMUA High on Gate and SMUB High on Drain.


nMOSFET_transferecurve.py

This script requires the Keithley 2600 Python library. Save this in your working directory.

In the figure shown below, the square root of the Source-Drain current is shown as a function of the Gate-Source voltage at different Drain-Source voltage. At first, a steep exponential increase can be observed at around 3,5-4,5 V (Gate-Source voltage). Followed by a flattened curve for higher voltages, marking the saturation region.

Data
The measured data is given in the textbox below. The first column is Gate Source voltage in V and the second column is the sqaure root of the Source-Drain current in A for a Drain-Source voltage of 0.001 V. Then respected columns of voltage (in V) and current follow for increasing Drain-Source voltage: 0.01 V, 0.05 V, 0.075 V, 0.1 V.