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Calculate lower cut off frequency for given circuit.

$\beta$ = 80, r $\pi$ = 1.3 k $\Omega$ Gm = 50 $\mu$A/v c$\pi$ = 15 pf c$\mu$ = 1 $\mu$ f (a) Fls for cs. ![enter image description here][1] Fls = $\frac{1}{2\pi Tcs}$ = ${1}{2 \pi Req.cs}$ Req = Rs + (r$\pi$ ll Rth) Rth = (7k ll 4.2 k) = 2.625 k $\Omega$ Req = 100 $\Omega$ + [2.625 k $\Omega$ ll 1.3 k $\Omega$] Req = 100 $\Omega$ + 869.426 $\Omega$ Req = 969.426 $\Omega$ Fls = $\frac{1}{(2 \pi ) (969.42) (10\mu)}$ Fls = 16.417 Hz → (1) (b) Flcc = $\frac{1}{2\pi TCcc}$ = $\frac{1}{2\pi ReqCC2}$ Req = Rc + Rl = 5k + 5k = 10k Flcc = $\frac{1}{(2 \pi ) (10 \pi )(2\mu)}$ = 7.96Hz → (2) ( c ) flce, Flcc = $\frac{1}{2\pi Tce}$ = $\frac{1}{2\pi Reqce}$ Req = $\frac{(Rs ll Rth) + r \pi}{(1+\beta)}$ ll RE = $\frac{(96.33 + 1.3k}{81)}$ ll 300

Flce = 16.303 Hz → (3)

The lower cut off frequency is 16.417 Hz.

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