written 3.5 years ago by |
Answer: Step 1 : Calculate the value of k :
$k=\dfrac{I_D(on)}{[V_{GS}(on)-V_{TH}]^2}$
$\therefore k=\dfrac{6\times 10^{-3}}{(8-3)^2}$
$\therefore k=0.24 \times 10^{-3}A/V^2$...................(1)
Step 2 : obtain $I_{DQ}$
$I_D=k[V_{GS}-V_{TH}]^2$..........................(2)
Now , $V_{GS}=V_{DD}-I_DR_D$
$V_{GS}=12-I_DR_D$......................(3)
Putting the value of (1) and (3) in (2),
But $R_D=2k=2000 \Omega$
$\therefore I_D=0.24 \times 10^{-3}[9-2000I_D]^2$
$\therefore I_D=0.24 \times 10^{-3}[81-36 \times 10^3I_D+4 \times 10^6I_D^2]$
$\therefore I_D=0.01944-8.64 \times I_D+960I_D^2 $
$\therefore 960I_D^2-9.64I_D+0.01944=0$
Solving the above quadratic equation ,we get
$\therefore I_D=7.24mA \ or \ I_D=2.79mA$
Now $I_D\neq7.24mA$ because if $I_D=7.24mA$ the value of $V_{DS}$ becomes negative.
Hence , $I_{DQ}=2.79mA$
Step 3 : Calculate $V_{DSQ}$
$V_{DSQ}=V_{DD}-I_DR_D$
$\therefore V_{DSQ}=12-(2.79 \times 2)$
$\therefore V_{DSQ}=6.42 V$