Unexpectedly High 'id' Current Value in N-Channel MOSFET Simulation using Simulink

Hello everyone,

I am currently simulating the characteristics of an N-channel MOSFET using the Simulink Simscape library. Specifically, I am referencing the ee_mosfet example provided.

Here are the simulation parameters:

• Gate input signal: Square wave with an amplitude of 24V and a frequency of 20 kHz.
• Vds input voltage: Constant at 12V.

With these settings, I am observing an 'id' current value of 16,000A, which seems unusually high.

Could anyone shed light on the potential reasons for this observation? Additionally, any suggestions on how to obtain a more realistic 'id' current value would be greatly appreciated.

Thank you in advance!

Answer 1

[Joel Van Sickel]

Hello, I tried recreating your simulation and got a current of 800 amps, which while not your 16000, is still quite high. Have you changed the device parameters at all? The basic transistor model will let you drive a transistor at a much higher gate voltage that a real device could actually handle, allowing it's on resistance to become much smaller than would be realistic. This will only happen if you apply an unrealistic gate voltage, or paramaterize the device to behave ideally. As there is no resistance modeled in this example, you could theoretically have infinite current if you parameterized the components correctly to allow near 0 on resistance. The device in this example is expected to be driven at a much lower gate voltage.

[ズイード]

Thank you for your answer. I was able to solve the issue by adding line resistance and inducatance to the circuit.