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(ELEC102)final_pastf.pdf
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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
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(a)
(b)
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Text Box: (a) Name two advantages of MOSFET. (b) Draw the cross sectional diagram for an enhancement NMOSFET and describe ve
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1
(c)
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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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3
(b)
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(2)
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(c)
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(d)
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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)
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t =0
1ms
2ms
2V
-2V
0
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(a)
C=1F
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4
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(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)
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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)
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(4)
Text Box: Draw the cross sectional structure of a NPN BJT transistor operated in the amplifier mode. Describe the movement of
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7
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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
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RC = 1k.
RB = 1k.
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RE = 200.
(a)
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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)
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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