Please provide working steps with values, explainantion and final answer. Thanks

Question

Please provide working steps with values, explainantion and final answer. Thanks.

In the two-stage amplifier circuit shown in Fig. 8-1. assume that the npn BJT and the NMOS have the following device parameters: VA = 100 V and beta = 100 for the BJT. Q1 Kn = 2m A/v2, VTHN = 1V; lambda n = 0.001 and no body effect for the MOSFET, M1.Identify the configuration of each stage of the multi-stage amplifier. [4 marks] Design Re1 and Re2: to obtain Ic,q1 = Id,m1 = 1 mA [8 marks] Calculate the small signal parameters for O1 and M1. [5 marks] Write down the overall gain expression in terms of small signal parameters of the tranistors and circuit components, i.e.,v0/v5 [8 marks] Choose RD such that the overall gain is 3. [5 marks]

Explanation / Answer

a>

the BJT is common collctor amplifier and the mosfet is common drain amplifier.

b>

the dc bias at the base of BJT,

Vb=10*45/(45+55)=4.5 V

so the base current,

Ib=(4.5-.7)/(B*Re1)

Ic=B*Ib=1 mA

solving,

Re1=3.8 Kohm

the dc bias voltage at the gate of the mosfet,

Vg=10-(Ic*3)=7V

the voltage drop in the resistor Re2,

=Id*Re2

Id=1mA

so, Vgs=7-Id*Re2

Id=k*(Vgs-Vtn)^2

Id=2*(6-Re2)^2

Re2=5.3 Kohm

c>

for the BJT,

r_pi=.026/Ib=2.6 Kohm

r_pi*gm=100=B

gm=38.46 mA/V

for mosfet,

gm=2*sqrt(k*Id)=2.82 mA/V

Rout=1/(lambda*Id)=1000 Kohm [very high resistance close to infinity]

d>

the gain of the BJT,

R_bi=r_pi+Re*(1+B)=386.4 Kohm

Ri=Ra1 || Rb1 || R_bi=23.2 Kohm

gain A1=-(Rc/Re1)*(Ri/(Ri+Rs))=.756

the gain of the mosfet,

A2=-(Rout || Rl ||Rd)=-(10 || Rd)

total gain=.756*(10 || Rd)

e>

.756*(10 || Rd)=3

10|| Rd=4

Rd=6.67 Kohm

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