written 2.6 years ago by |
1) Fixed Bias ckt
Applying kvc in $c_1 - s \ ckt$
$-V_{GG} - I_G \ R_G - V_{as} = 0$
But $I_G = 0$
$\therefore V_{as} = -V_{GG}$
- Drain current is given as.
$I_D = K_n (V_{as }- V_{Tn})^2$
Applying kyl in D - S ckt
VDD - ID RD - VDS = 0
VDS = VDD - ID RD
2) Self bias.
Applying KVL in g-s ckt
-IGRG - VAS - IDRS = 0
But IG = 0
$\therefore$ $V-{as} $- -ID RS.
Putting this in equation of ID.
$ID = Kn \ (V_{as} = VTn)^2$
Solving this to get value of iD.
Applying KVL in D.S ckt
VDS = VDD - ID ( RD + RS)
3) Voltage divider bias.
VGs = VG - VS.
VG = $\frac{VDD \ R2}{R_1 + R_2}$ VS = Id RS
$\therefore$ $V_{as} = \frac{VDDR2}{R_1 + R_2}$ -Id RS
Putting the expression of $V_{as}$ in the equation of ID
$I_D = K_n (V_{as} = VTn)^2$
Solving above equation to get value of ID.
Applying KVL in D-S ckt
VDD - ID RD - Vos - ID RD = 0
VDS = VDD - Id (RD + RJ)
Given
$\theta_{JA}$ = 1.2˚ c/w
$\theta_{JC}$ = 0.5˚ c/w
$\theta_{cs}$ = 0.5˚ c/w
Tamb = 40˚ c
Tj(max) = 200˚ c
PD(max) = $\frac{Tdev - Tamb}{\theta \ sk + \theta \ jc + \theta \ cs}$
$\frac{200 - 40}{0.5 + 0.5 + 1.2}$
PD(max) = 72.72 w
For Hartely OSC
f = $\frac{1}{2\pi \ \sqrt {Leq \ C}}$
Leq = $L_1 + L_2$ = 2mH
c = 0.2 $\mu$f
f = $\frac{1}{2 \ \pi $\sqrt {2mH x 0.2 \mu \ f}}$ $f_2 \ 8 KH_z$