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**Unformatted text preview: **ECE 230B, HW-2, Winter 2010 Solutions 1. When the gate voltage greatly exceeds the threshold for strong inversion, a first-order solution of s ( V g ) can be obtained from the coupled equations, Eqs. (2.195) and (2.182), by keeping only the inversion charge term. Show that s B ox g fb B si a kT q C V V kTN +-- 2 2 2 2 ln ( ) under these circumstances. Estimate how much s can be higher than 2 B by substituting some typical values in the logarithmic expression. Solution: By keeping only the dominant inversion charge term in Eq. (2.182) and substituting it in Eq. (2.195), one obtains V V kTN C n N e g fb s si a ox i a q kT s = + + 2 2 / . When V g increases beyond the point where s = 2 B , most of that increase appears as inversion charge in the third term. There is very little change in the band bending beyond s = 2 B . A good approximate solution for s is then obtained by letting s = 2 B for the second term and solving s from the third term:...

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