1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Quick PMOS question

  1. Oct 13, 2006 #1
    I have a PMOS transistor circuit set up.

    These are my parameters:

    Vthreshold = -0.4 V
    Vgs = -3 V

    Vgt = Vgs - Vthreshold = -3 + 0.4 = -2.6 V

    Vds = Vgs - Vthreshold = -2.6V

    I'm trying to figure out what operating region this stupid thing is in. There are so many different ways of figuring this out, that it's getting very confusing -- it seems every source uses a different notation.

    I know it's not in the Cutoff region, because Vgs < Vthreshold. However, since Vds and Vgt are the same, how do I decide if it is in Linear or Saturation region?

    For linear: Vgs < Vthreshold and Vds > Vgt

    For saturation: Vgs < Vthreshold and Vds < Vgt

    This is really starting to bug me.

    If I could figure out how to find Vgd -- that is, voltage from gate to drain, I might be able to figure something out. However, my Vin = 2V and the drain is connected to a variable resistor and then to ground, I think Vgd = 2V. But I don't think this is possible since it's a PMOS, so I'm ignoring that parameter for now.

    Thank you.
     
  2. jcsd
  3. Oct 31, 2006 #2
    what is Vgt? never have come across this....
    The voltages around MOSFET usually have this relation Vgs = Vgd + Vds. So, I don't think that you can get Vds the way you did.
    To determine the region of operation you need to look at inequality of this sort: Vds ? (Vgs - Vtp)
    However Vds is not given.... so you'd either have to know extra parameters like Id, W/L or assume a value/region and then verify.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Quick PMOS question
  1. Quick question (Replies: 3)

  2. Quick logic questions (Replies: 5)

Loading...