AMZ Mosfet Boost Output Impedance?

[bwanasonic]

Jack's Mosfet Boost article mentions that the output impedance is "moderately low" . How low is it? What variables effect it?

Thanks
Kerry M

[R.G.]

The output impedance of any bipolar or FET common emitter/source amplifier is about equal to the collector/drain resistor. The collector/drain itself is quite high impedance, megohms, and so it hardly lowers the impedance of the resistor at all.

In all mos fet boosters like this, it's effectively the drain resistor, so 2.7K on this one.