This is a screenshot of IRF9640 MOSFET datasheet. Will you please tell me, what is meant by max and min value of Vgs threshold voltage. Also what they mean by test condition.
Whether the max and min values are only applicable for specified test condition?
What will be the threshold voltage for a switching circuit and how the range varies?
My doubt is, for p channel mosfet to turn on Vgs < Vgs(th). For IRF9640 in what volt it will turn on -3 or -5? When i used in my application Vs is 6v and Vg is 3v hence Vgs=-3v but it won't turned on, Why? It turned on when Vgs=-3.3v.
If we consider -2v as threshold, it should turn on when Vgs=-3v. Why they given a range for threshold voltage. Whether we have to test each mosfet to know their threshold. What i am pointing is that, if we have two IRF9640, will Vgs(th) is differ from each other?
Best Answer
This means that the threshold voltage between the Gate and Source is between -2V and -4V, meaning the Gate must be between 2-4V lower than the Source in order for it to be in it's 'on' state.
The third column on your screenshot is the test conditions, as it says in the datasheet. If you are doing a switching circuit, just make it a nice 5V circuit, that way you are more than covered, stick a pull-down or pull-up resistor on the gate and switch the 5V to turn it on and off.
Being above the maximum, you can be sure that this way, the MOSFET will be turning fully on and off each time it is switched.