Question

$\text{Consider the n-channel and p-channel MOSFETs, if these are to have equal drain currents}\text{when operated in the saturation mode with overdrive voltages of the same magnitude.}\text{Then the ratio of width of p-channel MOSFET to n-channel MOSFET is\_\_\_\_\_\_}\text{(Assume,}{\mu }_p=0.4{\mu }_n,L_n=L_p)$

• A. 2.5

Answer 1

The correct option is A 2.5
$\text{Since two MOSFETs are operated in saturation mode,}{I}_{DN}={\mu }_n{C}_{ox}\frac{W_n}{2L}(V_{GSN}-V_{TN}{)}^2\text{or,}{I}_{DN}={\mu }_n{C}_{ox}\frac{W_n}{2L}(V_{OV}{)}^2\text{where, overdrive voltage}{V}_{OV}=V_{GSN}-V_{TN}\text{Similarly,}{I}_{DP}={\mu }_p{C}_{ox}\frac{W_p}{2L}(V_{OV}{)}^2\text{where overdrive voltage}{V}_{OV}=V_{GSP}-V_{TP}\text{given,}{I}_{DN}=I_{DP}{\mu }_n{C}_{ox}\frac{W_n}{2L}(V_{OV}{)}^2={\mu }_p{C}_{ox}\frac{W_p}{2L}(V_{OV}{)}^2\therefore \frac{W_n}{W_p}=\frac{{\mu }_p}{{\mu }_n}=0.4\text{In the given question, it is asking that,}\frac{W_p}{W_n}=\frac{1}{0.4}=2.5$