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University Mhamed Bougara ,Boumerdes

Institute of Electrical and Electronic Engineering

Department of Electronics

Done by

-Oussama Gassab -hammouya houssam - Achraf Djerida

Groupe 01

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n communication we have to perform some conditions on

the signals in order to transmit or receive them , like

modulating , demodulating and filtering , to do that we have

to build required circuits with specified precision and conditions

.

n order to build the needed circuits for the needed

communication application we have to do the theoretical

analysis by doing the mathematical calculations which

applies the physical formulation of the devices , and that

analysis simulated by using a software , if the results in the

simulator are matches the mathematical analysis , than the

circuit can be built in the real world in order to perform its

required job.

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-Single transistor ampli f iers

Objectives :

1- to learn how to bias and test a transistor amplifiers

We have the following circuit :

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The mathematical analysis :

= = 10 51 = 5And when we take = 50+300

2= 175 we have

= 5.7 . 103

so

=

=

100.655.7 .103

=

1.64Multisim simulation :

We got the following results

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Measuring the gain voltage = ( ) ( ) = 1921 = 192

When change the transistor BJT-NPN-VIRTUAL we got

When we change the transistor the beta is changed and all

the Q points it has been changed , in that circuit the changing on

beta will correspond high change to collector current . so in this

case the transistor base current is unstable relative to the

changing of beta , in addition the beta factor is sensitive to

temperature and even to the current inside the transistor , that is

mean the collector current is unstable at all . so this bias is not

practical because it is not stable .

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Part 02 :

The mathematical analysis

= 1 = 11 = 1 = =104.51

1= 4.5

1 = 39 2 = 8.2

The gain is A= 174

When change the transistor to BJT_NPN_VIRTUAL

We have got the following result

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So the gain is = 119.7070.999594 = 119.8We see that the gain is approximetly for the first one and the Q

points are nearly the same so this bias stabilize the Q points and

it is applicable . so the emitter resistor stabilize the Q point for

the changing of beta

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Part 03 :

We have the following circuit :

The mathematical analysis

We have computed by using the fact that1 = = = 1 = 100651 = 9.35And for maximum symmetrical swing = 2

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= = 2 = 102 1 = 5 By using the oscilloscope we have got the following

So the gain = 214,038 1.375 = 155.66When increase the voltage to 20 mv we have the following

Result .

Explaining this distortion .

We know that the transistor is saturated when Vce is less than We have = ()

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And since

>

|

| 100 = 105 > 100 All the conditions of the approximation are satisfied so we

expect a results that matches the thoery models .

When we perform the ac analysis we got

So at resonance frequencies the impedance is 17.1075 k

which matches the theory 20k

And the bandwidth is about 8.6445 which and the theory

band width is 5kHz

When we build the equivalent RLC circuit as follow

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The ac analysis for this circuit is

So the results matches the equivalent circuit the bandwidth

is 7.5131 kHz as shown above

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t is very easy to perform the theoretical analysis in

papers by using only the mathematical formulas , and

that what we have accustomed to do . about us we

have an experiment to deal only with papers , pan , and

calculators to solve a problem , and we thought that the

problem it has been solved , but in reality we found thatwe have solved only mathematical formulas , and to

simulate that in the simulator there are many concepts

must realized and many ideas must performed .

hat is mean to put a such application in real world

we have to recognize many things that correspond

with losses and errors and approximations. Wehave learnt that the engineer must have experience in the

field with real appliances not only the theoretical formulas

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