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Doctor of MOSFET Health

I’ve been thinking about MOSFETs. They are as vital to our modern way of life as oxygen. They truly are, think about it. They are all around us, quietly doing their jobs so efficiently that we take them for granted.

It amuses me to think of my fellow engineers as doctors—and our patients are the humble MOSFETs.

By engineers, I mean all of us. Even the most esoteric, high-order software engineers have a role. For example, you might be writing code in C#, F# or Haskell, but the memory and logic elements are made from MOSFETs and your code has an effect on the power dissipated. You might not be thinking about this, but someone did and implemented power management to make sure the code does not break the hardware. To be effective, we must work at the right level of abstraction, but always keep in mind, for whatever you are doing, there are MOSFETS under the hood toiling away at your command, sometimes many millions of them.

We engineers are responsible for their care and feeding. Because of the importance of the designs we work on, this is a task to be taken seriously.

The doctor’s role depends on the task at hand. For the masses of MOSFETS in digital domains, the task is easier and much of the burden is carried by the silicon vendor who makes sure the losses due to leakage, switching and conduction are under control as long as the engineer honors the guidance of the datasheet, application notes and common sense.

For analog power engineers, we’re directly responsible for managing FET stresses and making sure all the corner conditions are understood and don’t represent excess hazards. And, we have to worry about other types of transistors like IGBTs, bipolars and upcoming flavors of SiC and GaN, all with their particular quirks and dietary requirements.

This might seem like a frivolous take on things, but I’m deadly serious. There should be a Hippocratic Oath for engineers.

Raise your right hand and solemnly swear…

I call to witness and swear by [insert your preferred holy spirit]: I will observe and keep an oath to manage the health of the MOSFETs in my care to the utmost of my knowledge, power and judgment.

Amen.

Do you have stories to tell about the care and feeding of your pet MOSFETs? Tell us about your victories and sad tales of woe in the comment section.

1 comment on “Doctor of MOSFET Health

  1. zeeglen
    November 23, 2015

    When connecting a scope probe to the gate of a MOSFET in an ungrounded DUT, always connect the scope probe ground wire first. Even if you are wearing heel straps or a wrist strap.

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