PMOS Body Diode Voltage Drop

Discussion in 'General Electronics Chat' started by Tony J, May 9, 2015.

  1. Tony J

    Thread Starter New Member

    Dec 3, 2014
    4
    0
    Hi,

    I am working with a p-channel mosfet to source a load. I have simulated this in ltspice but I'm skeptical of the results. The datasheet shows Vsd forward voltage of the zener body diode being -1.2v but when I simulate this circuit I don't see a drop of 1.2v from the source to drain. Should I only pay attention to the Rds(on) and calculate the voltage drop by using the supplied current multiplied by the Rds(on)? I have the schematic and the simulation results attached. Thanks!

    Link to IRLML6401 datasheet: http://www.irf.com/product-info/datasheets/data/irlml6401.pdf
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,056
    3,245
    The 1.2V diode drop is for a diode current of 1.3A.
    The Rds value will indeed start to take precedence when Vgs exceeds the gate threshold voltage of about 0.5V
    Why didn't you show your results?
     
    Last edited: May 9, 2015
  3. Tony J

    Thread Starter New Member

    Dec 3, 2014
    4
    0
    Thanks for the reply. I forgot to attach the circuit and simulation results. I have them attached here. The pmos will be in saturation since the Vgs will exceed the gate threshold voltage. So the body diode's affects are mostly used for the linear region of the mosfet?
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,056
    3,245
    Normally the body diode is reverse biased and has no affect on the drain-source voltage or current.
     
    Last edited: May 9, 2015
Loading...