what is the use of this resistor??

Discussion in 'The Projects Forum' started by onlyvinod56, Oct 24, 2009.

  1. onlyvinod56

    Thread Starter Active Member

    Oct 14, 2008
    362
    1
    hello everyone....

    - first check the attachment please.....
    - it is an inverter....
    - 220 ohm resistors are connected from pins 10 & 11 to the gates of the mosfets...
    - IC 4047 is given from a 12v supply.... so the output voltage pulse at 10 & 11 will be 12 (or less but not more...right)
    - see the next attachment...the Vgs of IRF 540 is 20v...
    if i give the 12v directly to the mosfet...then also it'll work in safe range
    then what is the use of 220ohm....
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    The 220 ohm resistors prevent the Mosfets from oscillating at a VHF frequency due to their gate capacitance and inductance of their input wires. The 220 ohm resistors should be mounted as close as possible to the gate pins of the Mosfets.
     
  3. onlyvinod56

    Thread Starter Active Member

    Oct 14, 2008
    362
    1
    thankyou audioguru...

    how can i calculate the resistor value for different mosfets at different applications......

    what parameters i have to concentrate.....???
    any example.......please....
    thankyou
     
  4. shortbus

    AAC Fanatic!

    Sep 30, 2009
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  5. SgtWookie

    Expert

    Jul 17, 2007
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  6. onlyvinod56

    Thread Starter Active Member

    Oct 14, 2008
    362
    1
    thankyou shortbus.....
    my doubt is cleared
     
  7. onlyvinod56

    Thread Starter Active Member

    Oct 14, 2008
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