Help needed understanding a MOSFET chart

Discussion in 'General Electronics Chat' started by Xelectro, Aug 13, 2012.

  1. Xelectro

    Thread Starter New Member

    Aug 12, 2012
    1
    0
    Hi
    I am currently experimenting with a power MOSFET IRF510
    And I am trying to understand how to properly read the output characteristic chart, to determine required Vth to bias the MOSFET drain at half rail voltage (class A amp).
    Vcc 12v
    Rload 24R
    Id (max) 500ma
    Desired id at bussing 250ma
    Need help understanding the chart.
    Thanks
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,014
    3,234
    Because of the large unit-to-unit variation of Vth you can't use that by itself to bias the transistor at 1/2 the supply voltage. Thus a resistor is typically added between the transistor source and ground to swamp out the Vth variations and give a more stable bias point. Since this resistor also reduces the transistor gain you can bypass it with a capacitor to increase the gain for AC signals. Here is a discussion of biasing.
     
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