If it says 5V Gate to Source then you know it is a logic level device.
Most mosfets that are NOT "logic level" will show Rdson measurement conditions of Vgs = 10V or so,
Vth is nothing to do with a mosfet being switch on. A Vth of 5V means it is fully _off_ at 5V or below.
The states 'on' and 'off' are binary in nature, so if you have one you dont have the other, and if you have the other than you dont have the first.
In other words, if something turns off at 5v then it also turns on at 5v.
Sometimes Vth is used to show when the device will turn on.
it is sometimes used to show the minimum voltage that will turn the device on at least a little.
So if i say "logic level" maybe i am referring to the CMOS logic level with a 15v supply.
That is true, but it doesn't apply to a FET which is not a binary device.No, that doesn't happen even with a binary device, and as I said the FET is not a binary device.No it is never used like this.Yes, it is ALWAYS used to show that. It is where the device STARTS to turn on.You might be but the rest of the world does not use that term to mean that. When used in isolation the words "logic levels" referrer simply to TTL logic levels. Any other meaning of "logic levels" has to be accompanied by a qualifier.
It means that that 5v threshold is USED as a binary set.
It doesnt matter that it really is or not, it matters what we take it to be in theory.
But here is what Wikipedia has to say about it:START_QUOTEThe threshold voltage, commonly abbreviated as Vth or VGS (th), of a field-effect transistor (FET) is the minimum gate-to-source voltage differential that is needed to create a conducting path between the source and drain terminals.END_QUOTE
Twaddle.And that is crap. And who could find fault with that? However your leap that this means the FET is in any way "on" is something I would argue with. That "conducting path" could very well have a resistance of say 1M, and that would not imply by any means the FET was on.The threshold voltage parameter plays no part in being able to determine if a FET can be used at TTL logic levels as a switch. Go and ruin your own devices if you want but don't peddle crap to beginners on this forum.
I guess we cant have a reasonable conversation
I've had no trouble with this explanation since the late 1980's.
and i wont be able to believe you in the future either.
Funny how can we know this when Vth cant be used for anything, according to you.
The threshold voltage parameter plays no part in being able to determine if a FET can be used at TTL logic levels as a switch.
Day and Night form a binary pair that we can use in reasoning
I guess we cant have a reasonable conversation here as you think you know everything so go ahead, but dont tell me what to do because your wasting your time.I've had no trouble with this explanation since the late 1980's. If you want to knock it that's up to you, but dont tell me what is crap and what isnt because i wont believe you now, and i wont be able to believe you in the future either.By your own statements, if you have a Vth of 5v then you cant use it for 'logic level' applications because it may only be 'on' by 1MOhm.. Funny how can we know this when Vth cant be used for anything, according to you.