Chapter 7, Problem 7.9TYU

An n−channel MOSFET has parameters $K_n=0.4{\text{mA/V}}^2$ , $V_{TN}=1\text{V}$ , and $\lambda =0$ . (a) Determine the maximum source resistance such that the transconductance is reduced by no more than 20 percent from its ideal value when $V_{GS}=3\text{V}$ .(b) Using the value of $r_s$ calculated in part (a), determine how much $g_m$ is reducedfrom its ideal value when $V_{GS}=5\text{V}$ . (Ans. (a) $r_s=156\text{Ω}$ , (b) 33.3%)