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(ELEC102)final_pastf.pdf
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(16)

ID

IS

source usually shorted to body

Metallic film

IG= 0
ID= IS

An NMOSFET consists of a metal gateinsulated from a p-type semiconductorsubstrate (or body) by an insulating layer of silicon dioxide. On either side of the gate there are n type regions forming the drain and source.

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1

(4)

(a)

(b)

(1)




Text Box: (a) Name two advantages of MOSFET. (b) Draw the cross sectional diagram for an enhancement NMOSFET and describe ve


(14)

(4)

1

(c)

(2)



Text Box: Hence NMOS is triode since1. VGS > VT 2. VDS < VGS .V VT
Text Box: VGS = 2V


Text Box: In the circuit, find the MOSFET constant K . Show clearly your reasons . (14)Given that VT = 1V. At triode r

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2V

1k.

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Vo

1k.

Assume 2 NMOS are in saturation

2







Text Box: Find Vo . Show clearly your reasons. (23)

Text Box: Hence NMOS is saturate since1. VGS > VT 2. VDS > VGS .V VT



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(6)

3

(b)

(5)

(2)

(4)

(c)

(6)

(d)

(4)

(4)

(3)

(6)


Text Box: (a) Find the conductivity of intrinsic (pure) silicon (Si). Find also the resistivity. (b) The pure
Text Box: P-type

Text Box: III-V compoundGaAs, InP etc


Text Box: P or As.

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4

(i) If X = 1k., Y = 2k., draw the waveform of Vo.
(ii)If X = 1F, Y = 1k.. derive the equation for the output voltage VO, and hence draw the waveform of VO.


Assume theop amp is ideal. (21)

(5)

t =0

1ms

2ms

2V

-2V

0

(9)

(a)

C=1F

(7)







(11)

(8)

4

(3)

(b)

Text Box: Find the complex transfer function G (= V2 / V1 ) in terms of R, C, R2 and jw .Is the ideal op amp circuit a low pa

Text Box: Circuit is a high pass filter


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5

(b)

(2)

(5)

(5)




6

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e

1. EBJunction is a forward bias (on) diodeand BC is reverse bias (off) diode
2. E is very heavily doped(N +for NPN). E has many electrons,
3. B is very thin. So most electronsinjected from E (to B) are attracted to C and

(a)

(7)

(4)

Text Box: Draw the cross sectional structure of a NPN BJT transistor operated in the amplifier mode. Describe the movement of





(24)

7

(11)

9.7V

(b)

(a)

(2)



Text Box: Find the mode of the BJT.If VB = 5.7V, find IC/IB. Show clearly your reasons. For the BJT, given VBE(ON) = 0.7V,
Text Box: IB = 0.5mA




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8

(4)

RC = 1k.

RB = 1k.

(10)

RE = 200.

(a)

(6)


Text Box: (a) Draw the small signal (AC) equivalent circuit of the BJT amplifier and find the voltage gain Av ( = v1 / v2 ).

Text Box: v1


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8

(b)

(8)

Text Box: V2 = IB RB + VBE(ON) + IERE~ VBE(ON) + . IBRE ~ constant (= VB) Hence IC = . IB is almost a constant
Text Box: Since VB ~ constantHence IC .^ , IE *RE .^ , VBEON .` , IC .`IC is almost a constant
Text Bo