Electronics Lab Reports

8/10/2019 Electronics Lab Reports

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College of Engineering

Ateneo de Naga University

ECEM312 Electronics 1 Laboratory 1 of 5

Activity 1

Diode Characteristic and Biasing

Name: ____________________________________

____________________________________

____________________________________ Date Performed: ____________

Section: _________ Date Submitted: ____________

Laboratory Instructor: _____________________________________

RESULTS AND ANALYSIS

Table 1 Diode Specification

Product Number: 1N4001

Continuous Forward Current: 1 amp

Peak Inverse Voltage: 50 volts

Table 2 Diode Curve

Supply Voltage Diode Voltage

Diode and Resistor

Current (mA) Resistor Voltage

0V 0V 0

0.1 0.1 0 0

0.2 0.2 0 0

0.3 0.299 0 0

0.4 0.39 0 0.09

0.5 0.451 0.04 0.049

0.6 0.486 0.11 0.113

0.7 0.511 0.19 0.190

0.8 0.530 0.27 0.27

0.9 0.541 0.36 0.357

1 0.553 0.45 0.445

1.5 0.586 0.92 0.908

2 0.608 1.40 1.389

2.5 0.623 1.89 1.869

3 0.634 2.38 2.361


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OBSERVATION AND ANALYSIS:

The ratio V/I for the diode is not constant for each value of the source voltage while that

of the resistor is almost constant, close to the value 1000. At Vinput of 0.5 V, the diode V-I ratiois 11,275 while the resistors is 1,225. On the other hand, with Vinput of 0.9 V, the diodes ratio

is 1,502.78 and the resistors is 991.67. It could be inferred from these data that the inherent

resistance of the diode decreases as voltage across it increases while that of the resistor is

almost constant. It can also be seen that the voltage across the diode almost remains constant

even if the current through it increases.

Table 3 Diode Circuit

VABStates of

DiodeDiode Voltage Diode Current Bias Condition

Fig. 2 5 volts ON 0.65 3.68 FORWARD

Fig. 3 -5 volts OFF 4.96 0 REVERSE

Fig. 4 -2 volts OFF -2.045 0 REVERSE

Fig. 5 -3 volts ON -0.587 1.23 FORWARD

Fig. 6 -1 volt OFF -1.01 0 REVERSE

Fig. 7 1.5 volt ON 0.676 6.9 FORWARD

OBSERVATION:

Data suggests that when a positive potential is applied across the anode and a negative

potential across the cathode, it becomes forward biased and conducts current. It doesnt

conduct when the reverse happens. However, another condition which must be considered is

the diodes threshold voltage. To conduct, the voltage across must be equal to or greater than

this value. In the forward biased mode, the diode voltage is 0.58-0.68 volts while in the reversebiased mode it is equal to the single equivalent input voltage.


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Table 4

Faults VO condition (in terms of VCC)

1. Normal Condition Vd2Vcc + Vd1V(R1 ll R2)

2. R3 short Vd1

3.

R3 open Vd2Vcc + V(R1 ll R2)4. R2 short Vd1Vd2

5. R2 open VccVr1Vd1

6. R1 short VccVd1

7. R1 opens Vd2Vr2Vd1

8. D1 open 0 volts

9. D2 open VccVr1Vd1

Generalization:

Diodes are one-way conductors, allowing current in only one direction. When a diodes

threshold potential is met and voltage is applied across it in such a way that the cathode is

more negative than the anode, then it is said to be forward biased and it conducts an increasing

current at a constant voltage. If the terminals of the applied potential are reversed, the diode

resists conduction, has a non-constant voltage across it, and is said to be reverse biased.


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Activity 2

LED Characteristic

Name: ____________________________________

____________________________________

____________________________________ Date Performed: ____________




Table 1 LED Characteristics

Supply Voltage Diode Voltage Diode Current Luminous intensity

0 0 0 0

0.1 V 0.102 V 0 0.2 LUX

0.6 0.597 0 0.2

1.1 1.1 0 0.2

1.6 1.593 0 0.2

2.1 1.803 0.21 mA 0.3

2.6 1.856 0.74 0.7

3.1 1.887 1.20 1.3

3.6 1.913 1.66 1.2

4.1 1.937 2.13 3.7

4.6 1.956 2.7 4.8

5.1 1.971 3.15 6.0

5.6 1.98 3.66 8.2

6.1 2.007 4.19 9.7

6.6 2.02 4.68 11.3

7.1 2.032 5.15 12.9

7.6 2.047 5.67 14.5

8.1 2.061 6.16 16.1

8.6 2.075 6.67 17.7

9.1 2.088 7.16 19.2

9.6 2.101 7.66 20.8

10.1 2.115 8.16 22.4

10.6 2.127 8.65 24.0

11.1 2.140 9.16 25.5

11.6 2.153 9.67 26.1

12.1 2.165 10.17 27.3


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12.6 2.177 10.61 28.7

13.1 2.189 11.16 29.4

13.6 2.202 11.65 30.2

14.1 2.213 12.17 31.3

14.6 2.225 12.64 32.1

15.1 2.238 13.22 33.0

15.6 2.250 13.73 33.9

16.1 2.262 14.23 35.2

16.6 2.273 14.75 36.4

17.1 2.285 15.28 37.6

17.6 2.296 15.79 38.7

18.1 2.309 16.31 39.9

18.6 2.321 16.87 41.1

19.1 2.332 17.38 42.3

19.6 2.345 17.93 42.8

20.1 2.356 18.46 43.2

20.6 2.368 18.99 44.1

21.1 2.379 19.50 44.6

21.6 2.391 20.05 45.5


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OBSERVATION:

The LED V-I graph shows a very similar feature with the diode V-I graph in Activity 1. Like

the diode graph, this one shows the behavior of a forward biased LED, only that the threshold

potential is about 1.8 Volts compared to the diodes 0.7 Volts. This graph also shows a non-

linear non-constant relationship between LED current and voltage.


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This graph suggests an approximately linear relationship between LED current and

luminous intensity. This is also suggested by the current-luminosity ratio which almost remains

constant. It could be inferred that a LEDs luminosity is current -dependent and not affected by

voltage across.

GENERALIZATION:

As its name and the data suggests, an LED acts similarly to the semiconducting diode of

Activity 1. Its only other function lies in the fact that it emits light regardless of the threshold

potential across it. It emits light almost directly proportional with the current. However, even if

it doesnt conduct current, it emits light.


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Follow-Up Activity:


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Activity 3

Zener Diode Characteristic and Voltage Regulation

Name: ________________________________________________________________________

____________________________________ Date Performed: ____________



Table 1 Diode Specification

Zener Diode Parameters Rated Value

Part Numbers 1N4737A

Rated Voltage (VZ) 7.5

Rated Power (PZ) 1.0 W

Rated Maximum Current (IZM) 121 mA

90% of IZMAX 108.9 mA

Table 2 Zener Diode Characteristic Curve

VinZener and Resistor

CurrentResistor Voltage

Voltage across

Zener Diode

0V 0A 0V 0V

103 mV 0 0 102.8 mV

303 mV 0 0 302.2

0.505 V 0 3.7 mV 502

0.703 V 0.12 mA 56.6 mV 0.640 V

0.904 V 0.24 213.4 0.688

1.104 V 0.85 0.394 V 0.707

1.302 V 1.25 0.581 0.718

1.505 V 1.67 0.775 0.727

1.703 2.08 0.968 0.733

1.902 2.5 1.158 0.739


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1.999 2.71 1.255 0.741

Vin Zener and Resistor

Current

Resistor Voltage Voltage across

Zener Diode

0V 0A 0V 0V

-0.501 V 0 0 -0.500 V

-1.503 V 0 0 -1.502 V

-2.503 V 0 0 -2.502 V

-3.500 V 0 0 -3.499 V

-4.51 V 0 0 -4.51 V

-5.50 V 0 0 -5.50 V

-6.50 V 0 0 -6.50 V

-7.50 V -1.14 mA -0.529 V -6.98 V

-8.50 V -3.20 mA -1.483 V -7.02 V

-9.50 V -5.30 mA -2.456 V -7.06 V

-10.50 V -7.41 mA -3.432 V -7.09 V

-11.50 V -9.53 mA -4.39 V -7.11 V

-12.00 V -10.59 mA -4.87 V -7.13 V

V-I plot

Forward Biased


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Reversed Biased


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In the forward biased mode, the curves for the Zener diode and the PN junction diode

are similar as can be seen in the curve of Fig. 2. Both have zero currents at voltages below a

certain threshold and current exponentially increases as voltage passes that threshold. The

difference in characteristics between Zener and PN junction diodes can be seen in Fig. 4 in the

reverse biased mode. In said bias, the PN junction diode does not conduct current easily while

the Zener conducts exponentially after a certain threshold is reached. Another interesting

feature in this mode is that the Zener diode almost maintains a certain voltage after the reverse

threshold is reached, as seen in Fig. 4. The resistor remains approximately linear for both biases

as can be seen in Fig. 1.


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Table 3 Fixed Vi and Variable RL:

Vi = 15V ; RS = 560

RL VZ VRS VRL IRS IZ IRL

State

OfDiode

100 2.245 12.62 2.270 23.03 mA 0 23.03 mA OFF

220 4.22 10.74 4.22 19.44 0 19.44 OFF

330 5.53 9.44 5.53 17.09 0 17.06 OFF

470 6.76 8.21 6.76 14.85 0 14.84 OFF

560 7.47 7.49 7.03 14.34 1.57 13.51 ON

680 8.11 7.89 7.07 14.30 3.54 12.33 ON

820 8.46 7.12 7.09 14.26 5.37 11.02 ON

1K 9.54 7.39 7.12 14.18 6.89 8.88 ON


As Rl increases, the currents through Rs and Rl decrease while that through the Zener

diode increases after the diode turns on. However, the current through Rs remains

approximately constant after the diode turns on even if Rl increases. The load resistance


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Table 4 Fixed Rl and Variable Vi:

RS: 100R ; RL:1000

VIN VZ VRS VRL IRS, mA IZ, mA IRL, mA

State of

diodeOf

Diode

3.002V 2.729 2.718 2.729 2.78 0 2.77 OFF

4V 3.659 0.364 3.63 3.72 0 3.72 OFF

5V 4.55 0.456 4.55 4.66 0 4.66 OFF

6V 5.45 0.546 5.45 5.59 0 5.59 OFF

7V 6.37 0.639 6.37 6.53 0 6.53 OFF

8V 7.28 0.988 7.02 10.01 2.9 7.21 ON

9V 8.23 1.858 7.15 19.42 12.04 7.34 ON

10V 9.09 2.752 7.24 22.00 20.68 7.46 ON

11V 10.11 3.66 7.31 37.40 29.72 7.62 ON

12V 10.91 4.57 7.39 46.6 38.85 7.65 ON


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FOLLOW-UP ACTIVITIES

Circuit design:

FOLLOW-UP ACTIVITIES

Circuit design:

Circuit no. 1

The given circuit using the zener diode as a regular diode to get a voltage drop of 9V once it

passes the diode resulting to a output voltage of 3V which is the sum of the two AA size battery.

Circuit no.2

The given circuit used the zener diode as a voltage regulator, regulating the voltage to 3V which

is equivalent to two AA size batteries.


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Activity Number 5

Diode Application: Clamper Circuit

Name: ________________________________________________________________________

____________________________________ Date Performed: ____________




Design Values :

R : ______________ C: __________

Table 5 Output Characteristic

Clamping

Direction

Peak Output

during (+)

Cycle

Peak Output

during (-) Cycle

Type of Clamper

Fig. 1 downward 0.6 V -10.55 V Negative clipperFig. 2 upward 10.50 V -0.7 V Positive clipper

Fig. 3 downward 2.20 V -9.10 V Negative clipper

Fig. 4 upward 11.90 V 0.7 V Positive clipper

Fig. 5 downward -0.75 V -11.85 V Negative clipper

Fig. 6 upward 9.10 V -2.30 V Positve clipper


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Waveform 1

Waveform 2


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Waveform 3

Waveform 4


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Waveform 5


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Waveform 6

Follow-up Activity


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GENERALIZATION:

The basic components required for a clipping circuit are an ideal diode and a resistor.

In order to fix the clipping level to the desired amount, a dc battery must also be

included. When the diode is forward biased, it acts as a closed switch, and when it is reverse

biased, it acts as an open switch. Different levels of clipping can be obtained by varying the

amount of voltage of the battery and also interchanging the positions of the diode and resistor.

Depending on the features of the diode, the positive or negative region of the input signal is

clipped off and accordingly the diode clippers may be positive or negative clippers.


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Activity 6

Power Supply: Rectifier and Filter

Name: ____________________________________

____________________________________

____________________________________ Date Performed: ____________




Table 1 Rectifier

TYPE OF

RECTIFIER

AC Content DC Content

INPUT VOLTAGEOUTPUT

VOLTAGEINPUT VOLTAGE

OUTPUT

VOLTAGE

HALF-WAVE 12V 6.17V 0V 5.08V

FULL WAVE 12V 5.14V 0V 10.054V

BRIDGE

RECTIFIER12V 5.033 V 0V 9.36V

OBSERVATIONS AND ANALYSIS:

There is a difference in the reading of the rectifier before and after, this is due to the

fact that a certain positive voltage in the anode of the diode was only allowed to pass. There

will be an open circuit if a positive charge will be passed on the cathode of the diode used in the

rectifier. We can also observe here the difference of AC and DC measurement, where AC

measures the VRMS of the waveform produce by the rectifier. On the other hand, DC


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measurement measures the average on the waveform. This experiment also provides us the

fact that in a Half-wave Rectifier, AC value is greater than the DC value. DC value was divided

into two in a certain cycle. In a Full-wave, DC now is greater than the AC value. The value of DC

was multiplied into two in a certain cycle. We can also see from the data and result of theexperiment that a Full-wave rectifier has a higher output due to its two positive cycles

produced and seen in its waveform than the output produce in a Bridge Rectifier.

Table 2 Effect of Filter Capacitor in Half Wave Rectifier

DMM

AC FUNCTION DC FUNCTION

INPUT

VOLTAGE

OUTPUT

VOLTAGE

INPUT

VOLTAGE

OUTPUT

VOLTAGE

10F 12V 3.42V 0V 9.94V

100F 12V 672.9mV 0V 15.06V

1000F 12V 74.08mV 0V 16.05V

Table 3 Effect of Filter Capacitor in Full Wave Center Tapped Rectifier

DMM


INPUTVOLTAGE

OUTPUTVOLTAGE

INPUTVOLTAGE

OUTPUTVOLTAGE

10F 12V 2.21V 0V 13.12V

100F 12V 336.7mV 0V 15.58V


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1000F 12V 36.49mV 0V 15.89V

Table 4 Effect of Filter Capacitor in Full Wave Bridge Rectifier

DMM


INPUT

VOLTAGE

OUTPUT

VOLTAGE

INPUT

VOLTAGE

OUTPUT

VOLTAGE

10F 12V 2.091V 0V 12.88V

100F 12V 320.9mV 0V 15.01 V

1000F 12V 34.60V 0V 15.34V

Waveform 1 Half Wave Rectifier


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Waveform 2 CT Full Wave Rectifier


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Waveform 3 Bridge Full wave rectifier


As shown in the graphs above, we can see that the peak value of the waveform

decreases its voltage value until such time that the output of the rectifier without a capacitor

rises again, then the waveform will start rise up again. Ripple voltage were really seen in the

waveforms of the graphed values of the data gathered in the experiment. These are the

voltage variation at the output. The value of AC decreases when a capacitor was connected in

the circuit. When this happens, the DC value increases and lessens the ripple effect in the

output waveform. While decreasing the peak to peak voltage the average value the DC output

value increases.


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Follow-Up Activity:

According to the graph below, if the load resistance decreases the output waveform ripple

voltage will also increase.

Generalization:

Rectification is the conversion of alternating current (AC) to direct current (DC). A half-

wave rectifier is a circuit that allows only one half-cycle of the AC voltage waveform to be

applied to the load, resulting in one non-alternating polarity across it. The resulting DC

delivered to the load "pulsates" significantly. A full-wave rectifier is a circuit that converts both

half-cycles of the AC voltage waveform to an unbroken series of voltage pulses of the same

polarity. The resulting DC delivered to the load doesn't "pulsate" as much. As you increase the

value of the capacitor near the load, you also increase the value of the DC output.


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Activity 7

Bipolar Junction Transistor Fundamentals

Name: ____________________________________

____________________________________

____________________________________ Date Performed: ____________



Table 6 Transistor Specification

Parameters Value

Product Code 2Sc2655

HFE(min, typ,max) 70,0,240

ICmax, 2A

VCEO 50V

VCEsat 0.5V

VBEsat 1.2V

Table 2 Transistor Current Gain

Q1 Q2

IB IC IE HFE IB IC IE HFE

0.5 3.9uA 941.47uA 947.219uA 4.8 uA 119.8uA 94.9uA 24.9583

1 45.96uA 9.54mA 9.574mA 40.3uA 7.72mA 7.39mA 191.5633

2 142.11uA 27.8mA 27.118mA 137.7uA 29.55mA 29.80mA 214.5969

3 240.25uA 43.07mA 43.27mA 235.4uA 52.2mA 53mA 221.7502

4 339.28uA 57.87mA 58.207mA 334.9uA 77.8mA 76.4mA 232.3018

5 437.87uA 71.67mA 72.667mA 432uA 97.8mA 98.1mA 226.3889


As we can observe in the table above, table 1. The values of the emitter current is

approximately to the sum of the collector current and the base current in each assigned value

of , the increasing value of . As the increasing value of the, the Hfe (beta)


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decreases as observe or suggested by the gathered data. We can therefore conclude that the

Hfe (beta) transistor is not constant for the gathered values of emitter current and base

current.

In this experiment, we are actually expecting that values of the Hfe (beta) in transistor is

not a constant value because we are changing the value of that can cause to the values of

the base current, collector current, and emitter current so our Hfe (beta) will also change.

Table 3 Value of beta with constants VCE

VCE= 2V VCE = 4V

IB IC HFE IB IC HFE

2 0 2.018pA 0A 0 4 0 4.023pA 0A 0

2.10 0.5 11.546uA 932.587uA 80.77 4.10 0.5 55.511nA 5.329uA 95.999

2.3 1.0 33.64uA 2.81mA 83.532 4.3 1.0 33.64uA 3mA 89.18

3.66 1.5 81.268uA 6.913mA 85.064 4.85 1.5 81.268uA 7.392mA 90.958

4.44 2.0 129.896uA 11.185mA 86.107 5.2 2.0 129.896uA 11.896mA 91.58

5.2 2.5 179.19uA 15.431mA 86.115 5.8 2.5 179.19uA 16.549mA 92.354


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When the is adjusted to produce the desired, sets of the desired parameters are

measured. When the is adjusted to a higher value, the currents such as the base current,

collector current and the base currents are increasing in magnitude as well. But if you

determine the value of hfe (beta) value is decreasing in magnitude opposite to the process

observed when the is adjusted to a higher value.

The aforementioned statements of observations are true for . The same

statements of observation will be as of the same effect as that of .


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GENERALIZATION:

Even though the is set in the different values, the needed parameter is proportional

to the increase or decrease of the such as the emitter current, collector current and the

base current.

As hfe (beta) is to be determine, it is inversely proportional to the increase or decrease

of the determining factors such as , and

Follow-Up Activty:

Checking a NPN or PNP transistor

For a NPN transistor:

1.

Connect the collector leg to the positive lead and the base leg to the negative lead. The

analog tester should measure and give you a high resistance.

2. Connect the emitter leg to the positive lead and the base leg again to the negative leg.

The resulting measurements should be similar to (1).

3. This time reverse the connections. Collector negative lead; Base positive leg. This

will yield a low measurement of resistance. Reverse the connections stated in (2) to

also acquire a low value of resistance.

4. If items 1 up to 3 have been done without any error, it means that your NPN transistor is

functional.

For a PNP transistor:

Same as the instructions on NPN transistor checking HOWEVER the base should be

connected to the positive lead to check for the high resistance and to the negative to

check for the low resistance. If results match to the one stated here, then your PNP

transistor is functional.


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Activity 8

BJT Operating Region

Name: ____________________________________

____________________________________

____________________________________ Date Performed: ____________



RESULTS ANS ANALYSIS


Parameters Value

Product Number/Code MPS2222A

HFE(min, typ, max) 100 - 300

VCEO 40 V

Collector Continuous Current or ICmax 600 mA

VCEsat 0.6 V - 0.3 V

VBEsat 1.2 V

Table 2 Operating Region

VBB IB IC IE VCE VBE VCB

0 V 0 mA 0 mA 0 mA 15 V 0 V 15V

1.007 V 0 mA 128.69 mA 128.18 mA 8.976 V 0.75V 8.225V

2.007 V 0 mA 300.813 mA 303.205 mA 861.82m V 0.81V 50.652m V

3.010 V 4.353 mA 313.513 mA 317.876mA 264.412mV 0.83 V -569.024mV


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4V 6.299mA 313.871mA 320.17mA 248.053mV 0.85V -602.547mV

5.04V 8.347mA 314.054mA 322.4mA 239.482mV 0.87V -627.214mV

6V 10.239mA 314.162mA 324.40mA 234.41mV 0.88V -645.95mV

7V 12.213mA 314.243mA 326.46mA 230.59mV 0.89V -663.08mV

8V 14.89mA 314.305mA 328.49mA 227.67mV 0.91V -678.56mV

-1V 0 1.78A 23.943pA 15V -0.99V 16V

-2V 0 1.78A 24.273pA 15V -2V 17V

-3V 0 1.78A 25.504pA 15V -3V 18V


We observe the terminals of a BJT and see that the emitter-base junction is at least 0.6-

0.7 volts, the transistor is in the cutoff region. In cutoff, the transistor appears as an open circuit

between the collector and emitter terminals. Also, the transistor appears as an open circuit

between the collector and emitter terminals. We can also see that there is a certain point in

time where the base current has increased beyond the point where it can cause the collector

current flow to increase. The transistor is able to amplify small variations in the voltage present

on the base. The output is extracted at the collector. In the forward active state, the collector

current is proportional to the base current by a constant multiplier called beta,

The stated observations show the different operating regions of a BJT, namely: cut off,

saturation and forward active region.


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Table 3 Range of VBB for each operating region

Mode of operation Cut-off Active Saturation

Range of VBB

Table 4 Factor that affects Collector current

IC

Normal Condition (VCE=1/2 of VCC) 160mA, 7.48V

Different value of VCC 139.4mA,3.77V

Different value of RC 169.77mA,9.397 V

Effect of Temperature Lower value.


We can see the changes in the range of VBB in Table 3, which shows the differences of

the three operating regions of BJT. BJT design that affect IC: base material, nonuniform base

doping, nonuniform material composition, and the high-level injection effect. The said are the

ones which affects the values of Ic in the BJT circuit. We can see in the data that the values of Ic

are interrelated yet little discrepancies happen due to subtleties that it undergo.

GENERALIZATION:

There are three operating modes in BJT. The modes of BJT depends on hoe its junctions

Emitter-Base and Base-Collector are biased. First, the ACTIVE REGION, forward-biased in EB

Junction and reversed biased in BC Junction. Next, the Cut-Off Region which is under a reversed

biased condition in EB and BC Junction. On the other hand, under Saturation Condition, it is

both forward biased in EB and BC Junction. IC changes as the operating modes changes, its also

alters its values due to its different subtitles.


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FOLLOW-UP ACTIVITY:


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Activity 9

Bipolar Junction Transistor as Switch

Name: ____________________________________

____________________________________

____________________________________ Date Performed: ____________



RESULTS AND ANAYSIS


Parameters Value

PRODUCT Number 2sc2655

HFE( min, typ., max.) MIN: 70; TYP: N/A; MAX: 240

ICmax 1 A

VCEsat 0.5 V

VBEsat(min, max) 1.2 V

Transistor Inverter Design:

RC: 1.150 k = 1.2 k RB: 19.2 k = 20 k (potentiometer)

Table 2 Transistor LED Driver

Fig. 1 Fig. 2

VBB IC VCE LED state IC VCE LED state

0V 8.282 mA 2.061 V ON 0.00176 mA 10.99 V OFF

1V 8.294 mA 2.064 V ON 1.732 7.979 V ON

3V 9.429 mA 685.018 mV ON 8.141 169.696 mV ON

6V 9.903 mA 116.179 mV ON 8.193 107.328 mV ON10V 9.921 mA 94.475 mV ON 8.209 87.842 mV ON


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Given the figure 1 data in Table 2 we can see that VCE is inversely proportional with the value

of IC. This is due to how voltage supply increases, that the collector current increases and V CE

decreases. With VCEdecreasing, the base volatage is increasing. And since VCEis decreasing, the

light emitted by the LED is also decreasing until such time that it will turn off completely.

In Figure 2, just like in the output of Figure 1, the collector current increases and VCEdecreases

as the input voltage increases. However, the collector current and VCE in Figure 1 is greater

compared with the value of collector current in Figure 2.

The transistor is acting as a switch by turning on or turning off the LED. In the first figure, the

light of LED started from bright and eventually will turn off. On the other hand, in the second

figure, the LED is turned off from the start and increases its luminous intensity as the input

voltage increases.


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Waveform 1 Square Wave Input

Waveform 2 Sinusoidal Waveform


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GENERALIZATION:

Bipolar junction transistor also stands as a switch. It is like a closed switch when used in

saturated condition and it will act as open switch when it is in cut-off region. Aside from BJT

acting as a switch, it can also be used for LED drivers to operate.

FOLLOW-UP ACTIVITY: Design Problem


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Activity 10

BJT BIASING and BIASING STABILITY

Name: ____________________________________

____________________________________

____________________________________ Date Performed: ____________



RESULTS AND ANAYSIS


Values

Parameters Transistor 1 Transistor 2

PRODUCT Number/Code 2SC2655 MPS2222A

VCEO 50 V 40 V

HFE (min, typ., max.) 70,0,240 40

ICmax 1 A 600 mA

VCEsat 0.5 V 0.4 V

Table 2 BIAS STABILITY

Biasing

Techniques

Transistor 1:

_____2sc2655_________

Transistor 2:

______mps222a_________

IC VCE IC VCE

BASE BIAS (FIG.

1)2.833 mA 12.17 V 6.018 mA 8.98 V

EMITTER

FEEDBACK

BIAS (FIG. 2)

2.71 mA 12.172 V 5.482 mA 9.29 V

VOLTAGE

DIVIDER BIAS4.416 mA 10.398 V 5.08 mA 9.712 V


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(FIG. 3)

COLLECTOR

FEEDBACK

BIAS (FIG. 4)

2.40 mA 12.60 V 4.23 mA 10.77 V


The value of R4 was specifically given, then if a DC voltage source is applied. The values of IB and

IC will follow and also increase. But since the value of VCE is inversely proportional to IB and IC, then the

value of VCE will then be lessen or decrease.

Generalization:

A bipolar junction transistor, (BJT) is very versatile. It can be used in many ways, as an

amplifier, a switch or an oscillator and many other uses too. Before an input signal is applied its

operating conditions need to be set. This is achieved with a suitable bias circuit, some of which I

will describe. A bias circuit allows the operating conditions of a transistor to be defined, so that

it will operate over a pre-determined range. This is normally achieved by applying a small fixed

dc voltage to the input terminals of a transistor. Bias design can take a mathematical approach

or can be simplified using transistor characteristic curves. When the desired dc current and

voltage levels of the transistors have been identified, biasing circuits are constructed that will

set up the desired values of IC and VCE. It includes (state the biasing circuits). A biasing network

has to preferably make use of one power supply to bias both the junctions of the transistor.

The experiment was conducted to prove further and visually show this theory.


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Follow-Up Activity:

Circuit design:

Table 3 Computed and Measured value

Parameters IC VCE VE

Computed 5mA 7V 1V

Measured 5.24mA 6.618V 1.044V


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Activity 11

Bipolar Junction Transistor as AC Pre- Amplifiers

Name: ____________________________________

____________________________________

____________________________________ Date Performed: ____________




Table 9 Design Values

Transistor VCC HFE R1 R2 RC Re

2SC2655 15V 70 10k 1.5k 1.5k 200

Table 2 DC values

VCE VC VE VB IC

Computed

Values7V 8V 1V 1.7V 5mA

Measured

Values 6.618V 7.662V 1.044V 1.721V 5.24mA


The data gathered shows that they have the same input signal but they differ on their

output signals. This due to the change in source and the alternation in the output terminals.

The first output comes from the collector while the other comes from the emitter.


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Waveform 1 Output A

Waveform 3 Output B


As shown in the waveforms of the graph we can see that the gains are not the same.

The gain in output A is higher than the gain in output B. we can conclude that Output A is an

amplifier. The input waveform is the same for both outputs, but the output waves are different

because different errors and terminal where the data was gathered.


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Table 3 Amplifier Gain

VIOUTPUT A OUTPUT B

VO AV = (VO/VI) VO AV = (VO/VI)


As increase the input voltage, the output voltage in A will increase but on the other

hand B will decrease its value. The voltage gain in output A will increase and in B will decrease.

The waveform will change based on the changes of the input voltage in both outputs.

GENERALIZATION:

Amplification is the process of increasing the strength of an ac signal, that is, increasing

its power level. Amplifiers are circuits used to provide amplification. All amplifiers have

three fundamental properties; gain, input impedance, output impedance. The amplifier

input and output circuits combine to reduce the effective voltage gain of an amplifier from

its ideal value. The reduction in voltage gain caused by the amplifier input and output

circuits can be limited by increasing the value of Zinand decreasing the value of Zout.

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