Connect with us

MOS Capacitor

Discussion in 'Electronic Basics' started by Confused Soul, Sep 30, 2004.

Scroll to continue with content
  1. Hello Everyone,

    I wanted to know is there any way we can find the Threshold Voltage
    (Vt) and Flatband Voltage (Vfb) of a MOS capacitor from the CV
    characteristics of the MOS capacitor?

    Thanks
    ConfusedSoul
     
  2. Mantra

    Mantra Guest

    Vt only has meaning for a MOS*FET* but not a MOS*CAP*. It's a bit
    frightening if you don't already know that.

    You can measure Vfb using quasi-static (LF) CV and high-frequency CV
    plots. Strictly there are more variables than unknowns even then
    (flat band is a bit of a idealized theoretical concept rather than a
    real measureable phenomena) but you can get a usable value for
    engineering purposes. Again this is basic MOS theory 101 - first week
    of class, no less.

    Agilent, nee Hewlett-Packard, (e.g. 4140B/42XX) and Keithley make the
    appropriate instruments for this.

    MM
     
  3. Guest

    Guest Guest

    :> Hello Everyone,
    :>
    :> I wanted to know is there any way we can find the Threshold Voltage
    :> (Vt) and Flatband Voltage (Vfb) of a MOS capacitor from the CV
    :> characteristics of the MOS capacitor?
    :>
    :> Thanks
    :> ConfusedSoul

    : Vt only has meaning for a MOS*FET* but not a MOS*CAP*. It's a bit
    : frightening if you don't already know that.

    Absolutely not true.

    The capaciatance of a MOS CAP (MOSFET with its source and drain tied
    together) when the voltage across is less than Vt (i.e. no inversion channel)
    is very small (= Cgdo + Cgso where Cgdo and Ggso are small
    overlap capacitances.)

    When the voltage across the MOS CAP is larger than Vt, the channel
    is inverted, the device is in the linear region, and the Capacitance is
    approximately Cox * The Area of the Device (i.e. Much larger than Cgdo +
    Cgso.) If you understand this, you should be able to answer your own
    question now.

    Someone else can help you with your question about Vfb.

    Joe
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-