Faculty of Engineering

Electrical and Electronics Technology Laboratory

Lab :

i. Lab 9 : Verification of Ohm’s Law on Diodeii. Lab 10 : DC Analysis For Bipolar Junction Transistor ( BJT )

Lecturer : Dr. Nasri Sulaiman

Lecture Group : 3

Date : 18 March 2009

Name Matric number ContributionMas Nur Syairah Bt Muhamad Saad 150950 1. Type the lab report

2. Do the discussion and conclusion

Nurul Asmawanie Binti Ramli 150955 1. Do the result2. Do the calculation

Objectives

1. To determine voltage across diode and transistor.2. To determine operational range of a BJT.

Equipments and components

1. Resistor 220kΩ, 100kΩ, 1kΩ

2. BJT BC108

3. Transistor Q2N3904

4. AC voltage source

5. Capacitor 2×10µF

6. Function generator

7. Multimeter

8. Oscillpscope

9. Connecting wire

10. Breadboard

11. Computer with PSpice software

Procedures

AC voltage across diode and transistor

1. Construct the circuit as in Figure 1 below in.

Figure 1

2. The circuit is stimulated.

3. The results are observed.

4. Then, another circuit as shown in Figure 2 below is constructed.

Figure 2

5. The circuit is stimulated and the result is observed.

Vce

AC output signal

AC input signalC1

10µ

RB = 220kΩ RC = 1kΩ

Ib Ic

Vbe

B

C C2 = 10µ

E

Vcc = 9V

DC Analysis For Bipolar Junction Transistor ( BJT )

1. Circuit is assembled as shown below on breadboard. All terminal connections is ensured are correct. A transistor diagram and its symbol is draw.

2. 20 mVpp sinusoidal wave is applied at the AC input terminal.3. IB, I c, VCE, VB, VC, VBC is measured by using a multimeter. 4. The result is verified by the calculation.5. The AC output signal observed using oscilloscope is draw.

Results

AC voltage across diode and transistor

For Diode

Graph Idiode against V

For BJT Q2N3904

Graph IC against VCE

Graph IC against VBE

IC

IB

IE

IC

IE

IB

Transistor diagramTransistor symbol

DC Analysis For Bipolar Junction Transistor ( BJT )

For this experiment, transistor that we used is npn transistor

Transistor diagram and symbol

Experimental result:

a) IB = 0.0391 mA

b) IC = 1.6255 mA

c) VCE = 0.22 V

d) VB = 1.28 V

e) VC = 0.22 V

f) VBC = 4.0975 V

Calculated values:

n

p

n

i. VCC - IBRB - VBE = 0

IB=V CC−V BERB

¿ 9V−0.7V220000Ω

¿0.03772mA

ii. IC=β IBwhere β=100

¿100×0.03772mA

¿3.772mA

iii. V CE=V CC−ICRC

¿9V− (3.772mA×1000Ω )

¿5.228V

iv. V B=V CC−IBRB

¿9V− (0.03772mA×220000Ω )

¿0.7016V

v. V C=V CC−ICRC

¿9V− (3.772mA×1000Ω )

¿5.228V

vi. V BC=V CE−V BE

¿5.228V−0.7000

¿4.528V

Experimental result Calculated result Percentage

difference (%)

IB 0.0391 mA 0.03772mA 3.66

IC 1.6255 mA 3.772mA 56.91

VCE 0.22 V 5.228V 95.79

VB 1.28 V 0.7016V 82.44

VC 0.22 V 5.228V 95.79

VBC 4.0975 V 4.528V 9.51

The percentage difference between the experimental result

and the theoretical result

Percentage difference=Measured value−Calculated value

Calculated value×100%

Discussion

AC voltage across diode and transistor

1. For diode,the graph obtains from Spice show how the current varies when the voltage is

increasing.

2. The value of current is proportional to the voltage. It show forward biased when the AC

voltage range is bigger than zero. It show reverse bias when the AC voltage is decrease

to -100V and below.

3. For BJT Q2N3904,in this chart, you can see the cutoff region of operation in the area of

the chart with a steep slope. After this region is the nearly horizontal region of active

mode operation.

4. Ideally, the behavior of the chart in this region would be perfectly horizontal, but since

we are working with real components, nothing can be perfect.

DC Analysis For Bipolar Junction Transistor ( BJT )

1. The BJT is the most common transistor. It consists of three sections of semiconductors:

an emitter, a base and a collector. In an npn-type BJT, the emitter and the collector are

made of n-type semiconductors and the base is made of a p- type semiconductor. In a

pnp-type BJT, it is the other way round.

2. The three sections of a BJT form two p-n junctions: the emitter-base junction and the

collector-base junction. Individually, these junctions are not different from the p-n

junction in a diode.

3. The unique characteristics of the BJT originate from an interaction between these two

junctions.

4. The operating mode of a BJT depends on how its junctions are biased.

5. The BJT is biased to operate in the active mode in applications where it is used as an

amplifier.

6. In the cut-off and saturation modes, the BJT behaves like an open and closed switch,

respectively.

7. Most BJTs in digital circuits (logic gates, memory) operate in these two modes. The

reverse active mode is rarely used and is listed here for reference.

8. In a typical transistor circuit, the transistor is connected to an input circuit and an

output circuit or load. (Additional components are often necessary to bias the BJT).

9. One of the terminals of the BJT (E, B or C) is connected to both the input and the output

circuit.

10. The configuration of a BJT in a circuit is named after this common terminal. Thus, we

speak of common-emitter, common-base and common-collector configurations.

Schematic symbols for PNP- and NPN-type BJTs

Suggestion

1. The demonstrator must using LCD projector to show how to do the experiment.2. The electrical and electronic components must be prepare in good condition.3. The demonstrator must use the microphone to give the explanation.4. The value of the parts such as resistor, voltage source and others in the circuit should

be double checked before start the probe so that all parts have the values that are correct.

5. We should not depend fully on the voltage value given by the generator. Instead, we should double check the value with the multimeter to get a more accurate voltage reading.

Conclusions

AC voltage across diode and transistor

As a conclusion, by using Ohm’s Law we can measured and determined the value of

current, voltage and resistor on diode. The forward-bias and the reverse-bias properties of the

p-n junction imply that it can be used as a diode. A p-n junction diode allows electric charges to

flow in one direction, but not in the opposite direction; negative charges (electrons) can easily

flow through the junction from n to p but not from p to n and the reverse is true for holes.

DC Analysis For Bipolar Junction Transistor ( BJT )

From this experiment, we are able to determine operational range of bipolar junction transistor (BJT).

References

1. DC/AC Circuit and Electronics : Principles & ApplicationsRobert J. Herrick ( Purdue University West Lafayette, Indiana )Published by Thomson Delmar Learning, 2003.

2. Electronics Fundamental: Circuits, Devices and Applications, 7th Edition. Thomas L.FloydPublished by Pearson Prentice Hall. 2007

3. Lab manual EEE3100.4. Giorgio Rizzoni, Principle and Applications of Electrical Engineering,

McGraw Hill, fourth edition. 5. http://en.wikipedia.org/wiki/Bipolar_junction_transistor