P-Channel MOSFET Question..

Discussion in 'Homework Help' started by dortmundBVB, Apr 23, 2013.

  1. dortmundBVB

    Thread Starter New Member

    Apr 23, 2013
    3
    0
    http://imgur.com/Mhkm9vR

    Hey guys, I'm reviewing for a test and I'm stuck on this question (75)..

    The question is about a p-channel MOSFET with parameters K = -2mA/V^2 and VTR = -1.8 V connected to the circuit (of the picture in my link above). The R2 value is 5.6kohms and V2 = 1V..

    Find V1 required to set VDS to 8 V.

    I realize this is a p-channel MOSFET and both my K and VTR values are negative therefore I believe it is an Enhancement mode MOSFET stating that in the Constant Current Region : VDS < VGS - VTR

    However I can't seem to find a way to find V1 (or VGS) even by solving with KVL across loop 1 and 2..

    Any help would be greatly appreciated!
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,962
    1,097
    First you need to ask yourself. What is the voltage across R2 resistor if Vsd = 8V.
    And knowing R2 voltage, you can use Ohms law to find a drain current.
    Next you need to use this and solve for Vgs from this equation.
    Id = K*(Vgs - Vt)^2
     
    aws505 likes this.
  3. Jon_Snow

    New Member

    Jan 15, 2013
    16
    0
    There's an error in that problem. Vds = -8V not 8V.
     
    Last edited: Apr 25, 2013
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