Micro Eng said:
> given a circuit, as Bob described where the drain is the supply side,
> and the source has the load, for an N channel device would this ever
> really work since the Vgs that needs to be asserted for full turnon is
> being adjusted because as the voltage on the gate increases the voltage
> on the source will slowly rise.
>
> I put a circuit together using a IRLR3714, and even at 5V on the gate,
> could only get a little over 2V on the load using 4.5V on the drain
> connection.
>
> Did I miss something on the interpretation ?

The definition was for 1.2 volts in and 1.2 volts out with 5 volt gate drive.

Look at it this way. With a source follower circuit, the output will never
be more positive than gate voltage minus Vgs. But if your input(drain)
voltage is less than that, no problem, the FET is full on, and output is
connected to input.

That's why I suggested P-channel FETs for all the other voltages, and
N-channel for the 1.2V circuit.

-Bob

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