Very simple problem !

Discussion in 'Analog & Mixed-Signal Design' started by haji22, Oct 12, 2016.

  1. haji22

    Thread Starter New Member

    Dec 18, 2012
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    0
    I've just built a simple n-channel fet switch -Supply 5V
    S=0v
    G=15k to +5v
    D=1K to +5V

    Why is there a current flowing into the gate?
    I thought FETs were voltage controlled?
    I've also simulated this in Tina-TI - same result - Am I going loopy?
     
  2. BR-549

    Well-Known Member

    Sep 22, 2013
    1,980
    388
    How much gate current is there?
     
  3. crutschow

    Expert

    Mar 14, 2008
    12,974
    3,220
    Is this a junction FET or a MOSFET?
    An N-JFET will have gate current when the Vgs is positive, since it becomes a forward biased diode.
     
  4. haji22

    Thread Starter New Member

    Dec 18, 2012
    5
    0
    Its a 2n3822 JFET - Thanks all - I understand now.
     
  5. haji22

    Thread Starter New Member

    Dec 18, 2012
    5
    0
    I've just replaced it with MOSFET and all's as expected - Thanks again.
     
  6. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,669
    804
    Well, once in a while someone who can see their mistakes on their own, welcome to the forum :)
     
  7. haji22

    Thread Starter New Member

    Dec 18, 2012
    5
    0
    Thats whats so good about the internet - the whole world can help you!
     
  8. haji22

    Thread Starter New Member

    Dec 18, 2012
    5
    0
    And this forum of course!
     
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