Digi Anal5

GTHS KUMBO_Electrical Department_Fifth sequence exam…………….…………...…April.2011 1

SECTION ONE: TECHNOLOGY1.1 Give the meaning of the following abbreviations: PMOS, ECL, USB, ALU, RAM,

ROM, BIOS.

1.2 Do a comparative study of the TTL circuits and the CMOS logic circuits in terms

of: (i) Respond time; (ii) Supply voltage level; (iii) integration scale; (iv) cost;

(v) energy consumption.

1.3 How many flip-flops are needed to realize an asynchronous counter that counts

the seconds of a minute?

1.4 Give one application domain of each of the following electronic components:

Zener diode; Operational amplifier; TRIAC; DIAC; Capacitor, Resistor, Transistor,

Inductor.

1.5 Draw the three-diode equivalent circuit of a thyristor, and explain how this

component can be tested with a multitester.

1.6 Give the difference between asynchronous counter and synchronous counter.

1.7 Give one advantage and one disadvantage of MOS transistor over bipolar

transistor.

SECTION TWO: ANALOGUE CIRCUITSExercise 1: Alternating current.Consider the following AC network.

o

o

E

E

010

208

2

1

4

1

2

1

R

R

6

8

2

2

1

L

C

L

X

X

X

REPUBLIC OF CAMEROONPeace – Work – Fatherland

……………GTHS KUMBO/ ELECT DPT

FIFTH SEQUENCE EXAMClass: F36

Option: Electrotechnology

Duration: 04H

Coefficient: 4

Written paper

ELECTRICAL, DIGITAL AND INDUSTRIAL CIRCUITS

No document is allowed except the one given tothe candidates by the examiners.


E1 E2

R1

L1

R2

C

L2

Z1 Z2

Z3

A

B

IL

Exercise 2: DC current.Consider the DC network below.

R6 R7 R8

R5

R3 R4

E1

R1

E2

R2

A

B

C

Req

IL

3. Determine the Norton’s equivalent generator seen from the terminals A and C.

Deduce the current IL flowing in the load. Determine the current flowing in the

resistors R3, R5 and R6.

4. Using mesh analysis, calculate the currents I1 and I2 flowing in resistors R1

and R2 respectively.

5. What is the value of the load resistance that will permit a maximal power

transfer? Calculate that maximal power.

Exercise 3: Bipolar transistor.Consider the transistor amplifier circuit below.

R1 = 24kΩ; R2 =12kΩ; RC = 600Ω; R = 100Ω; RG = 8kΩ; 100

1. Calculate the impedances Z1, Z2 and

Z3.

2. Determine the Norton equivalent

generator seen from the terminals A

and B. Deduce the current IL

3. Determine the Thevenin’s equivalent

generator seen from the terminals A

and B. Deduce the voltage across Z3.

E1 = 10V; E2 = 5V; R1 = 5Ω; R2 = 10 Ω;

R3 = R4 = 20Ω; R5 = 10 Ω;

R6=R7=R8=30 Ω.

1. Determine the value of Req.

2. Determine the Thevenin’s

equivalent generator seen from the

terminals A and C. Deduce the

potential differences Vac and Vbc

respectively across AC and BC.


R G

C 1

2 2 0n

R 2

R 1

R C

R

C 2

B

M

+ V cc

v2

v1

B. Dynamic study.The dynamic parameters of the transistor at the quiescent point are the following:

r = 1kΩ; β = 100, .

1. Draw the ac equivalent circuit of the amplifier circuit.

2. Determine the equation of the dynamic load line and draw it in the (IC, VCE)

axis.

3. Determine the input resistance Re and the output resistance Rs of the

amplifier circuit.

4. Give the role and the name of capacitors C1 and C2.

Exercise 4: Operational amplifier

R1

R2

R3

OA1OA2

R5

R4u

STAGE 1 STAGE 2

v1

v2(t)

v3(V)

v3 = f(t)

1 2 3 4 5v3 v4

10

8

6

4

2

-10

A. Static study.The quiescent point of the transistor has the

following characteristics: AIB 500 ;

VVBE 6.00 .

1. Using Thevenin’s theorem, determine

the equivalent generator seen from

terminals B and M, which is used to

polarise the transistor.

2. Deduce the supply voltage Vcc and

VCE0.

3. Draw the static load line and represent

on it the quiescent point.


In the circuit on the figure above, the operational amplifiers are ideal and the circuit is

supplied by +12V and -12V.

A. Study of stage 1:If the operational amplifier operates in linear mode:

1. Express v3 in terms of v1, v2, R1, R2 and R3.

2. Give the expression of v3 in terms of v1 and v2 given that R1 = 4.7kΩ,

R2 = R3 = 10kΩ.

3. What condition must exist between R1, R2 and R3 to have V3 = -V1 – V2?

B. Study of stage 2:1. Is the amplifier operating in linear mode? Justify your answer.

2. If R4 = R5 = 5kΩ;

a. Express u in terms of v4.

b. If v3>u, what is the value of v4? What is the value of u?

c. If v3<u, what is the value of v4? What is the value of u?

3. v3 varies as shown on figure 3; draw the variation of v4 with time.

SECTION THREE: DIGITAL CIRCUITS1. Compute the binary operations: (i) 11011111+11111110;(ii) 1110101-1101111

2. The thermostat T of an electric iron operates following the combinational logic

function CBABCAABCAT . . (i) Draw the truth table of T. (ii) Simplify T

first by algebraic method and secondly using Karnaugh map. (iii) Draw the

logic diagram and the electric diagram of the simplified form of T.

3. How many flip-flops are needed to realise an asynchronous counter modulo

64? Draw its logic diagram.

4. The counter modulo 64 above is used to address EEPROM-type memory. The

frequency of the clock signal is 64 MHz. The length of a memory word is equal

to 4 bits. (i) What is the meaning of the abbreviation EEPROM? What is the

number of memory words in that memory? Determine the capacity of the

memory in terms bits and in tem of byte. An information coded as follows is to

be stored in that memory: 1111010111101001001111012. Convert that

information in hexadecimal and deduce the number of memory words that will

be used to store it.

SUBJECT MASTER: Mr. NGOUNE Jean-Paul,

PLET Electrotechnics, GTHS Kumbo

Digi Anal5

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