output impedance of common source amplifier

Yes, you divide out the micro. 1 S = 1/(1 ohm), 1 micro = 10^-6; just substitute that into the "5000 uS" expression, and solve.

Note that the forward transconductance changes with bias current; make sure you're using the right figure, and don't forget to account for device variation.

But the output impedance of a common *source* amplifier isn't 1/gm. That one is the output impedance of a common drain stage.

For a common source stage you use 1/go

Also note that parameters depend on the bias conditions and that those given in datasheets and suffixed by a 's', like gfs, gos, are at VGS=0 bias conditions.

And for a R loaded common source stage the output impedance is often dominated by the load resistor value.

-- Thanks, Fred.

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Thanks Fred.

My mistake - I meant common drain; I was thinking source follower.

And you sucked me right in, because that's what I was thinking, too.