Re: MOSFET question: Drive voltage vs. Vgs(th)


<accolade@xxxxxxxxx> wrote in message
news:1132078002.207502.207930@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> you'll see that the title says "2.5V Specified", which I understand
> refers to the drive voltage. However, under the "On Characteristics,"
> you'll see Vgs(th) min. = 0.4V and Vgs(th) max. = 1.5V. Why isn't
> Vgs(th) max. = 2.5V,

FETs are imperfect devices. Sure they turn on at Vgs but the higher the
ACTUAL gate drive voltage the lower the on-resistance. "2.5V Specified"
probably means that the on resistance and other parameters were
measured/specified with the gate at 2.5V.

Many FETs are designed for particular applications. For example you will
sometimes see FETs called "logic level" devices. This means that Vgs is low
enough for them to be driven by 3V or 5V CMOS logic families.


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