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(ELEC101)exam_pastd.pdf
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1

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(a)

(c)

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Text Box: (a) Show that the resistivity of intrinsic (pure) silicon (Si) is 2278 ..-m. (b) A silicon is doped with Indium (gr

Text Box: Hence dope Si with 5x1021 Indium/m3 .
Text Box: The resistivity of intrinsic Si

Text Box: Density of electrons is given by


Text Box: p-type Si


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2

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Text Box: Find VO / VS in terms of R, C and jw. If C = 1.YF , R1 = 1k.., R2 = 10k.., find the complex transfer function G


Text Box: Circuit is a high pass filter

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3

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(a)

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4

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(a)



Text Box: . In the ideal op amp circuit, the diode equation is . whe
Text Box: If V2 = - 0.62V D is a ON diode




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4

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VO= Vi + Vc = -10 C10= -20 V

Vc = -10V

3V

3V

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(b)



Text Box: (b) In the ideal diode circuit, find Vc and sketch Vo(t). Label clearly VO(t) . Assume the diode is ideal. (12)




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Text Box: (c) In the diode circuit, sketch and label clearly VO(t) . D2 is an ideal diode and D1 is an offset diode with
Text Box: VO



VZK = 7V

rZ = 5.

5

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6

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e

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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

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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VO(t)

RC

RB

Vi= 0.74V


Text Box: Given the BJT circuit below and the IC -VCE curve of the BJT. The Q point is chosen as IC = 18mA and VCE = 5V. (a)
Text Box: vi(t)


VCE2 = 6V

Draw load line,

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IB = 0.16mA

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(b)





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Text Box: (a) Find IC / IB . Given RE = 1k.. and Vi = 7V. Show clearly your reasons. For the BJT, given VBE(ON) = 0.





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RC = 1k.

RB = 1k.

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(b)


Text Box: . Draw the small signal (AC) equivalent circuit of the BJT amplifier and find the voltage gain AV ( = Vout / Vin





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9

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Text Box: (a) Use Boolean algebra to show that (9)


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9














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4.87510.100.1112

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9

P

Q

P

R

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Text Box: (c) Express decimal number 4.87510 into binary number. (6)



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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.