Part $2-$Structure $(30$ m $)$

Question $1$

An n$-$channel JFET in the amplifier circuit shown in Figure $1$ has transconductance factor, $g_m=2\mathrm{.}25$ mS and $Av=-4\mathrm{.}5.$ Solve high frequency response of $f_{Hi}$ and $f_{HO}$ if the internal capacitor given is $C_{Wi}=2\mathrm{.}5pF,C_{WO}=4pF,C_{gd}=1\mathrm{.}2pF,C_{gs}=4pF$ and $C_{ds}=0\mathrm{.}5pF.$

$(6$ marks$)$

ANALOGUE ELECTRONIC

TEN$10804$

Question $2$

The direct cascade multistage amplifier built using BJTs is shown in Figure $2$ below with the value of ${}_1=100$ and ${}_2=60$ respectively. Answer the following questions:

$($a$)$ Determine DC bias for voltage and current each stage.

$($b$)$ Redesign the circuit into an ac equivalent circuit.

$(12$ marks$)$

$(3$ marks$)$

$($c$)$ Analyze AC circuit to find the amplifier input and output impedance, $Z_i$ and $Z_o.$

$(3$ marks$)$

$($d$)$ Calculate voltage gain, $A_V$ for each stage and its overall voltage gain, $A_{VT}.$

$(6$ marks$)$