Connect with us

Mosfet not Switching the current to load

Discussion in 'General Electronics Discussion' started by Khan415, Jul 10, 2019.

Scroll to continue with content
  1. Khan415


    Jul 10, 2019
    ello everyone i am using a Mosfet for switching purpose..I have to use 3 volts power supply between drain and load as per requirement of my design.The current i required is 2.13 amps but with the 3 volts power supply it is supplying only 0.97 A.

    i am triggering the gate from a 555 timer as i need a dealy before swithing.The rating of mosfet is 9amps but is not giving the required current using 3 volts supply,Any Help?
  2. Alec_t


    Jul 7, 2015
    Welcome to EP!
    1) What is the exact type number of your 555? Unless you are using the CMOS variety the 555 output voltage will be about 1.2V below the supply voltage, i.e. will be only about 1.8V.
    2) A standard MOSFET needs a gate voltage (Vgs) of about 10V to turn on fully, so with only 1.8V it will not conduct fully. Even a 'logic'level' MOSFET might struggle. What is the rated Vgs(th) threshold turn-on voltage, as per the datasheet, for your particular MOSFET?
    Khan415 likes this.
  3. Audioguru


    Sep 24, 2016
    You are asking about your Mosfet and 555 timer but did not say what is their very important part numbers.

    1) Most Mosfets need a gate-source voltage of 10V to fully turn on. Logic level Mosfets need 4.5V to fully turn on. The part number on the datasheet says what it is.
    2) An ordinary old design LM555 or NE555 has a minimum supply of 4.5V look at its datasheet, and their output voltage does not go that high. You should be using a more modern Cmos LMC555, TLC555 or ICM7555 that have a minimum supply of 2V, but use a 4.5V supply the same as the logic level Mosfet.

    If you need to use your old parts then power the ordinary Mosfet and 555 with a 12V fairly low current supply then use the high current 3V for the load.
    Khan415 and Bluejets like this.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day