An Introduction to Depletion-Mode MOSFETs

Even though we publish new blogs daily from your intrepid editor and from a number of well-known writers, sometimes it's good to have a look back at some of our well received articles from the recent past. Here is one that ties in with my recent blog that discussed IGBTs and MOSFETs.

The article was written by Linden Harrison, at the time a technical writer for Advanced Linear Devices Inc. Linden briefly discusses the enhancement-mode MOSFET. In the case of an N-channel device, that's the version whereby you apply a positive voltage to the gate with respect to the source to enhance the conduction channel (turn it on).

The author then dives in to the depletion-mode devices, which work the other way: It's already on, and you apply a negative voltage to the gate to turn it off.

This is a solid article with plenty of good information on theory and with practical applications.

7 comments on “An Introduction to Depletion-Mode MOSFETs

  1. Michael Dunn
    February 26, 2013

    By pure coincidence, the rare depletion MOSFET came up in a recent blog about a cool & cheap little component tester: Clever Design Creates Rock-Bottom Component Tester

  2. Brad Albing
    February 26, 2013

    I saw that. It was coincidental. Still, a little extra discussion always helps w/ these parts. Too many engineers think that there are only NPN bipolar and N-channel enhancement mode MOSFETs.

  3. jkvasan
    February 26, 2013

    Nice article. 

    Also, if one of the bloggers can write about capacitors and the application of each type. For example, where we would use a polyester film capacitor, polypropylene one etc, could be discussed. Such a blog would jelp us in choosing the right capacitor for the application.

  4. Brad Albing
    February 26, 2013

    That's a good suggestion – I'll pursue that.

  5. Brian Dotson
    February 28, 2013

    Ditto! Thanks, Jay! I'd love to hear all about choosing the best capacitor dielectric type for the job!

  6. SunitaT
    February 28, 2013

    For example, where we would use a polyester film capacitor, polypropylene one etc, could be discussed.

    @Jayaraman, I agree with you. It would be great if we get articles on capacitor applications of different types. I would also wish if some blogges covers analog issues related to Analog layout's like matching, decoupling issues.

  7. amrutah
    February 28, 2013

    Yes,  in CMOS technology all devices that are present are the MOSFETS and vertical BJT's.  Though there are low VTH MOSFETS, but I dont understand why there are no Depletion-MOSFETS.  In case of current mirrors we can have one and help combat the headroom problem.  

    What is your take on using the depletion mode transistors for always ON current mirrors??

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