P-Channel MOSFET Question..

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

  1. dortmundBVB

    Thread Starter New Member

    Apr 23, 2013

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