محمد عبدالمنعم ابوالعل

 

King Saud University                                                    Faculty. of Engineering

 

Question 1

Check true or false , if false write a correction

 

1-     The bandwidth of the CC  amplifier is grater that that of CE amplifier with the same gain  .

2-     The efficiency of Class C power amplifier is independent of the conduction angle

3-      The transistor  mixers works in saturation region .

4-     For a given tuned amplifier the loaded quality factor is greater than the unloaded quality factor.

5-     The bandwidth of the amplifier depends on its class of operation .

 

Question 2

Choose the correct answer :

1-                             To increase the tuned amplifier bandwidth :

Decrease the tuning capacitor                Increase the coil inductance

Increase the load resistance .

2-                             The gain decreases as the  frequency increase  in

CE amplifier                  CC amplifier                            both CE and CB amplifiers   

3-                             The PLL  circuit is used in

ASK  detection                        FSK detection                  Both PM and FM detection

4-                             The conduction angle of a class  B amplifier

Less than 180               equal to 180                             grater than 180

5-                             To increase modulation index m_f  of a given FM signal

Decrease the VCO gain                        Increase the VCO gain

Use voltage amplifier before the VCO.

 

 

Question 3

a-      For the circuit shown in Fig .1 prove that :

the resonance frequency =  1/2p ( LC_eq) ^1/2  where C_eq is the series combination  of  C₁, C₂ , C₃ . Find the circuit quality factor and bandwidth . 

For the  oscillator circuit shown in fig.2 find an expression for the frequency of oscillation f _o then calculate :

1-     the frequency of oscillation

2-     The gain to sustain oscillation

3-     The circuit bandwidth

 

Question 4

Design a class C power amplifier used in AM transmitter working at 1 MHz . The power required in each side band is 2.5 W . The modulator works at 70% modulation index . The load is 50 W and coupled to the collector circuit using transformer with primary inductance = 1 m H . The amplitude of the carrier signal is 10 V and the circuit efficiency has to be > 85% .

 Define the following circuit component:

1- The dc power supply V_CC                            2- The biasing voltage

2-  The output transformer turns ratio    4- The transistor output resistance . 

 

Question 5

a-      What is the name of the circuit shown in Fig.3. Explain how it can be used in FM modulation and demodulation.  

b-     If C_D= 100 Pf  at  6 v and increases to 110 pf    when  the bias becomes 3 V . If the V_mod = 3 sin 628 t . Calculate the output signal modulation index m_f  .

c-      Show how you can modify the circuit to double  the modulation index .

 

 

 

 

بسم الله الرحمن الرحيم

King Saud University
College of Engineering

Electrical Engineering Department

EE 318: Electrical  and  electronic Circuits

First semester 1425/1426 ( 2004/2005)

Final Examination

Instructor: Prof. M. Abou elEla

 

 

اسم الطالب :-----------------------------------------

الرقم الجامعي :-----------------------------------------

 

Question 1  

Choose  the correct answer :

a-                 For the circuit shown in Fig.1

I1 = 4 ma                   3 mA                     2 mA

I2 = 2 mA                  3 mA                     5 mA

I3 = 1 mA                  0 mA                     2 mA

 

b-                The equivalent thevenin parameters between points a, b are

R_th = 4 kW                           1kW                                3kW

V_th = 8V                                        9V                                  6V

 

 

Question 2

Choose  the correct answer :

 

Given that w=1000 rad/sec L = 10 mH C1 = 100 mF C2 = 10 mF R = 100 W

The equivalent impedance between a, b is

Z= 111.1-  j10

Z= 111.1+ j10

Z= 100 W

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

: Question 2

Choose  the correct answer

a-For the circuit shown in Fig.3 the circuit function is

-         half wave rectifier                      Full wave rectifier

-         Switch                                      Non of the above

 

b-    If the input wave form is as shown in Fig.4-a

then choose the expected output waveform .

 

Question 4

Choose  the correct answer :

For the transistor circuit shown in Fig 5

IB = 46.5 mA                           4.65 mA                3 mA

Ic = 4.65 ma                             0.465 mA     0.3 mA

VCE = 5.35 V                          9.535 V                 9.7 V

 

The gain of the amplifier is approximately =

-160                                -150                      -185                      -180

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Question 5  

Choose  the correct answer :

a- The function of the circuit shown is

Inverting amplifier                     Non inverting Amplifier

Difference Amplifier                           Non of the above

 

 b- the voltage gain vo/ V2- V1    =

10                -10                        5                 -5

 

 

Question 6

Choose  the correct answer :

 a- The decimal equivalent value of the binary number  0110110 is

34                         44                         52                         54

 

b- The binary equivalent number of 69 is

1010100                                   01000101                        0110111

 

c- Draw the logic circuit used to realize the following logic function :

 

F= (A.B).((C+B).(A+D))