Bias Circuit

With the substitution of (4.11) in (7.11), the gain is
Equation 7.12
In modern integrated circuits, resistor RS will be replaced with a current-source output
resistance, which is significantly greater than RS. The source-follower gain is, in this case,
approximately (with no external load)
Equation 7.13
Parameter η will typically be in the range 0.1 < η < 0.2.
Note that the body effect degrades the "gain" significantly below the ideal unity. In the project
on the source-follower circuit, we measure the voltage transfer function of the source follower
for a range of dc drain current with body and source connected and with the body connected to
VSS. Τηε ρεσυλτινγ χυρϖεσ ωιλλ βε χοµπαρεδ το δεµονστρατε τηε βοδψ εφφεχτ ον τηε τρανσφερ φυνχτιον. Α
χυρϖε φιτ οφ τηε ΣΠΙΧΕ εθυατιον το µεασυρεδ δατα ωιλλ προϖιδε φορ αν αλτερνατιϖε δετερµινατιον οφ πα
ραµετερ γn. This value should be close to the value obtained from dc measurements.