UNIVERSITY OF BOTSWANA

FACULTY OF ENGINEERING AND TECHNOLOGY

DEPARTMENT OF ELECTRICAL DATES IN : WEDNESDAYS 6/13 APRIL 2016

AUTHOR: BOSA THEOPHILUS NTSHOLE

STUDENT NUMBER: 201301848

GROUP: 2

eeb 323 lab 2 bjt amplifier

ContentsOBJECTIVES..................................................................................................................................................3

EQUIPMENT USED.......................................................................................................................................3

INTRODUCTION...........................................................................................................................................3

PROCEDURE.................................................................................................................................................5

RESULTS AND ANALYSIS..............................................................................................................................6

SAMPLE OF CALCULATIONS.........................................................................................................................6

LOADLINE ANALYSIS....................................................................................................................................8

COMMENTS.................................................................................................................................................9

CONCLUSION...............................................................................................................................................9

REFFERENCES..............................................................................................................................................9

OBJECTIVESTo study the important properties of the software package Multisim 2001.

To study the performance of BJT amplifiers (Common Emitter voltage amplifiers).

EQUIPMENT USEDComputer system

Software package Multisim 2001

Hardware components

INTRODUCTIONMultisim 2001 is a complete system design tool that offers a very large component database, schematic entry, full analog/digital SPICE simulation, VHDL/Verilog HDL design entry and simulation, FPGA/CPLD synthesis, RF capabilities, Post processing features and seamless transfer to PCB layout packages such as Ultiboard from Electronics Workbench. It offers a single, easy to use graphical interface for all of design needs. Multisim 2001 provides all the advanced functionality one needs to take designs from specification to production. And because the program tightly integrates schematic capture, simulation, and programmable logic, one can design with confidence, knowing that they are free from the integration issues that often arise when exchanging data between applications from different persons or organizations.

If we consider the common emitter voltage amplifier, since β has very large variations by virtue of quiescent current, the temperature change and transistor replacement, the performance of the amplifier is beta-sensitive.

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Figure 1 : BJT VOLTAGE AMPLIFIERS CIRCUIT (CE)

Historically, first attempt to stabilize the Q point has to introduce the emitter resistor RE. There are two symmetrical supply sources in the circuit of positive source +Uc and negative source -UE.

It is known as the balanced supply with two equal rails, positive and negative. Where UIN =0 the output is equals to 0 too. Any quantity that changes UIN changes UE appearance, consequently;

RE includes the differential impedance of emitter junction (approximately 25mV/IE) and external resistor RE. Accordingly;

Therefore voltage gain does not depend on transistor parameters while beta is high. In this case we have a voltage amplifier.

PROCEDUREMultisim 2001 programme was launched on the computer. Then the electronic circuit provided below was connected as it appears. The function generator was connected at the input of the amplifier and was set as a sine wave generator that was operating at voltage amplitude of 10mV and frequency was set to 1KHz. The oscilloscope was connected at the amplifier’s input and output terminals and he signals were observed and measured at both input and output. Then the voltage gain of the amplifier was determined. Next the voltmeter was used to determine the voltage gain from there the results were compared. The parameters IB, IC, IE, VCB, VBE, VR1, VR2, VR3, VR4, IR1 and IR2 were then measured. The current gain βDC of the transistor was then determined. The same circuit was then connected using real hardware components and the currents and voltage drops were measured. The oscilloscope was connected at the amplifier’s input and output terminals and the input and output signals were observed and measured. The hardware voltage gain o the amplifier was then determined.

Figure 2: voltage amplifier circuit connection by multisim software

RESULTS AND ANALYSIS

Table 1: RESULTS

PARAMETER SIMULATED HARDWARE CAKCULATED

vi [mV] 7.071 10 10IB [µA] 7.785 8.40 9.23IC [mA] 2.002 2.00 2.38IE [mA] 2.010 2.00 2.38VCE [V] 5.981 3.376 3.576VCB [V] 5.294 2.719 2.8156VBE [V] 0.6874 0.6498 0.7VR1 [V] 11.299 10.886 10.73VR2 [V] 3.701 4.4028 4.304VR3 [V] 6.005 8.180 7.854VR4 [V] 3.014 3.7308 3.57IR1 [mA] 1.242 1.345 1.308IR2[mA] 1.234 1.3201 1.304vo [V] 1.299 2 2

SAMPLE OF CALCULATIONS

RTH = R1R2R1+R2 = =

3.3 X 8.23.3+8.2 = 2.35kΩ

VTH = V 2∗R2R1+R2 =

3.3X153.3+8.2 = 4.3 V

β DC=IcIb =

2.002mA7.785 µA = 257.16

VTH = IB RTH + VBE + (β+1) IB RE = IB (2.35 kΩ )+ 0.6874+ (257.16+1) IB (1.5 kΩ) = 4.3 V

IBQ = 9.23µA

ICQ = β IBQ =257.16 x 9.23 µA = 2.38 mA

VBE = 0.7 V

IE =( β+1) IB = (257.16 + 1) x 9.23 µA = 2.38mA

VCC = IC *Rc + VCE + IEQ *RE

VCE = VCC - IC *Rc - IEQ *RE = 3.576 V

Av (oscilloscope) = VoVi =

1.9V0.01 = 190 ,

Av (voltmeter) = VoVi =

1.2990.007071 = 184 ,

Av (hardware) = VoVi =

20.01 = 200

VR3 = IC *Rc = 2.38 x3.3 = 7.854 V

VR4 = IE*RE =2.38x1.5 = 3.57 V

VR1 = VCC - VR4 -VBE = (15- 0.7- 3.57)V= 10.73V

IR1 = VR1R1 =

10.7 3V8.2 kΩ =1.308mA

VR2 = Vcc∗R2R1+R2 =

15∗3.311.5 = 4.304V

IR2 = VR2R2 =

4.3043.3 = 1.304mA

LOADLINE ANALYSIS

ICsat = VccRc+ℜ =

153.3+1.5 = 3.125 mA

VCE =VCC = 15V

ICQ = 2.38 mA

IBQ = 9.23 µA

VCEQ = 3.576 V

S factor = (1 + β)/ (1+β) ℜRTH = (1+257.16) / (1+257.16) 1.5

2.35 = 1.57< 12

0 2 4 6 8 10 12 14 160

0.5

1

1.5

2

2.5

3

3.5

LOAD LINE ANALYSIS FOR BJT AMPLIFIER

voltage(V)

CURR

ENT(

mA)

COMMENTSBoth the simulation measured values, calculated and hardware values were close to each other in terms of magnitude. If the values of the voltage gains generated by all the instances were to be rounded they would all result to a common value with respect to the parameter of interest. Thus both hardware and simulation readings were accurate and precise, evidence can be derived from the amount/magnitude of errors obtained from all these values. The error is somewhat of less significance thus these values amounted to very small errors.

CONCLUSIONThe study of performance of BJT amplifiers with the very help of real hardware components was achieved. Also the study of more important properties of the software package Multisim 2001 was achieved. The voltage gain amounted by the hardware parameters is found to be 200 while the voltage gain amounted by the multisim software is found to be 190. Therefore the voltage gains are in the same range.

REFFERENCES- Introduction to electronic engineering.pdf- concepts-in-electric-circuits.pdf- multisim2001_Getstart.pdf (ISBN 1-55169-085-3 Rev. 3)