Quote:
Originally Posted by Generalx5
Also, theres something else im not really clear, is that, if a mosfet had already been turned on so that it conducts, and current is then applied at the source after. will the mosfet heat up? From what I've read, its the point when the mosfet conducts (rise/fall) when current is present at the source that heats up the mosfet. But say it the current wasnt there when it conducts, will that heat up the mosfet? The other thing is, will it even work if there is no current present at the source terminal?
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I'm not sure I competely understand your question.
The transistor will only heat up when there is current through it (just like anything else). P=IV; no current, not heat. In a MOSFET, all current is between the drain and source. So, Idrain=Isource. No source current means no drain current, which means no current at all.
To turn the transistor on, it must be biased correctly. The main part is that Vgs (gate to source voltage) must be above the threshold voltage for the transistor (usually a few volts). However, Vds (drain to source voltage) also needs to be higher than Vgs. I'd have to think about it a little more, but I don't think it's possible to properly bias it while also cutting the current.