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(ELEC102)test2_pastn.pdf
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(20)

(3)

1

(3)

(9)

(5)

(300)

Text Box: Find the voltage gain VO / VS in terms of R , R1 , R2 , C and j.. . If the maximum voltage gain is 11 and


Text Box: Circuit is a low pass filter

1

0

8V

t

-7V

4.5ms

(5)

(10)

(4)




(19)

2

(10)

(a)

(9)

(b)




3

(7)

(a)

VZK = 7V

rZ = 5.

(7)



Text Box: Model of zener diode
Text Box: . In the ideal op amp circuit, the diode has the reverse characteristics as shown. Given that the diode equation is




Text Box: model


(26)

(12)

(c)

(8)

(b)

(6)



Text Box: If V1 = 13V, D is a breakdown diode

Text Box: If V2 = - 0.62V D is a ON diode



(14)

4

(14)

Vc = -11V

-
VC
+

3V

+ VO -

C


Text Box: Vo = 3V

(26)

(14)

(12)

4

(c)





5

(16)

e

(10)

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





6

RC

RB

Vin (t)

Vi= 0.74V

+
VCE
-


Text Box: Given the BJT circuit and the IC - VCE curves of the BJT. (a) Draw the boundary of the cut-off, amplifier and



Boundary of the modes

IB = 0.12mA

IB = 0.08mA

Cutoff (or OFF)
Mode IB= 0

(7)

(7)

IB = 0.16mA

(a)


Text Box: a

Text Box: Amplifier (or active, linear) Mode VCE > VCESAT , IB > 0
Text Box: Saturation (or ON) Mode VCE = VCESAT

Vin1 = 0.76V
IB1= 0.12mA

Vin2 = 0.72V
IB2 = 0.04mA

Draw load line, Q point, and find voltage gain

(2)

(5)

(7)

(b)




(30)

(9)

(4)

(7)

(5)

(5)

(c)

(d)

(e)





Text Box: Maximum amplitude of Vo = 4V



Text Box: Q point = 14V

7

(8)

RC = 2k.

RB = 1k.

(8)

(25)

IC
(QorT)

VE
(QVE= IERE
~ ICRE)

VBE
(QVBE= Vin-VE )

IC
(QIC= IB )

IB

(9)

(a)

(b)


Text Box: (a) Explain briefly why the circuit can have stable IC if Vin is a constant . (b) Sketch the small signal (AC)



Text Box: Circuit can maintain stable IC (Q-point).





8

(20)



Text Box: . In the BJT circuit, . = 30, VBE(ON) = 0.7V, VCESAT = 0.2V Find IC/IB. Show clearly your reasons. (20)


Text Box: Hence BJT in saturation


(15)

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.

(10)

9

(5)

(a)

(b)




Text Box: (a) Name two advantages of MOSFET. (b) Draw the cross