+ Post New Thread
Results 1 to 2 of 2
  1. #1
    Advanced Member level 1
    Points: 2,937, Level: 12

    Join Date
    Mar 2015
    Posts
    467
    Helped
    3 / 3
    Points
    2,937
    Level
    12

    Drive P Channel Mosfet Using 8051

    Hi all.
    I am trying to Drive a 5V Solonied using 8051
    Circuit Attached.
    The gate of the Mosfet is not getting low. when i keep the mosfet OFF, it shows 5V at gate, but when i try to ON the mosfet using microcontroller 89S52, the voltage hardly drops to 3V, due to which my solonied does not gets active.

    - - - Updated - - -

    I am using 2 NPN Transistors to drive the Mosfet, because i need to invert the data.
    when the system reset initially, all the port pins of microcontroller get high, so i dont want the solonied to get active at this stage.

    •   AltAdvertisement

        
       

  2. #2
    Super Moderator
    Points: 77,678, Level: 67
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    15,748
    Helped
    3587 / 3587
    Points
    77,678
    Level
    67

    Re: Drive P Channel Mosfet Using 8051

    Hi.

    My recommendations:
    * use low side switching (easiest. Logic level N-CH)
    * or use high side power switch
    * or use one of the countless proven circuits given here in this forum and even more in the internet.

    your circuit:
    * no need to invert nor for a third transistor. Just use a pullup at the port pin.
    * show (supply) voltages in the schematic
    Every voltage measurement needs two points. When no other informatin is given then the voltage is meant to refer to GND.
    Thus I assume when you say "gate voltage" you mean "gate to GND voltage".
    But this is not how a MOSFET works. It switches ON/OFF by the value of "gate to source voltage"

    Drawing a schematic:
    * signal (information) flow is left to right
    * top are positive (supply) voltages
    * bottom are negative and GND voltages
    * add all informations for the function to the schematic (like supply voltage)
    This makes schematics more easy to read... and no need to switch between text and picture.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



--[[ ]]--