Group Members: Forrest Duplantier & Bach Nguyen

Professor George Durant

ET 225-01

Southeastern Louisiana University

December 10, 2015

Amplifier Project

I. Abstract

The term amplifier come from the Latin word ‘amplificare’, to enlarge or to expand.

Amplifiers or amps are electronic devices that can increase the power of a signal. The first

electronic device that can amplify a signal was the Audion(triode) vacuum tube, invented by Lee

De Forest, a Yale PhD graduate. By adding a control grid to Fleming’s two-element diode tube,

create the three-element vacuum tube used as an audio amplifier and oscillator for radio wave

generation. His first patented product was the improvement from Ruhmer and Bell with his

vacuum tube, he created a variable density sound on films process. For the next 50 years, the

vacuum tube was the only device that could amplify. This design of amplifiers didn’t change

until the invention of transistors. Instead of using triodes vacuum tubes, transistors were used for

most of the modern amplifiers.

II. Introduction

The most common usage for amplifiers are in speakers, audio amplifiers, home stereo or PA

systems. Bipolar junction transistors (BJTs) and metal oxide semiconductor field-effect

transistors (MOSFETs) are most common in modern transistors. In this project, we designed a

simple signal amplifiers using a bipolar junction transistor to amplify a 1 Hz signal required for

the project.

III. Objective

Our objective that we would like to achieve is to successfully design and adjust the amount

of resistance to precisely. By doing this we can achieve more understanding of amplifiers and

transistors using our knowledge that we have acquire in ET 225.

IV. Materials

- 3x10K Ω POTs

- 2x1K Ω POTs

- Jump wires

- 1xBipolar Junction Transistors

- 2xCapacitors 100µF

- 1xBreadboard

- 1x9V Power Source

- Elvis Machine

- Oscillator

- Signal Generator

V. Schematic

VI. Project’s Calculation

INPUTS CALCULATIONS

R1 2495 Ω mag Av = 4.9979

R2 1757Ω Vb = 3.718956 V

Rc 714Ω Rb = 1030.977Ω

Re1 142.86Ω Ic = 0.004193A

Re2 568.44Ω r'e = 5.962421Ω

Vcc 9V Zit = 33485.04Ω

βdc 200 Zis = 1000.182Ω

βac 225 Ib = 2.1E-05A

Q Point 3V Vce = 3.008908V

VII. Results

1. Peak input Voltage = 200 mV

2. Peak output Voltage(without the 1K Ω resistor) = 1000 mV

3. The value of measured Vce = 2.9 V & value of measured Ic = 3.78 mA. Compare to the

calculated counterpart Vce=3.0089V & Ic = 4.193 mA. The percentage error for Vce is

10% and for Ic is 9%

4. The gain is 5 times

VIII. Conclusion

We have successfully demonstrated and understand the project in amplifying 5 times

of the input voltage. Our measured Vce and Ic are a little smaller than the one we are

expecting to get from our calculations. But the amount of differences is under 10% which

is neglect able. The sources of errors could be in our equipment, the human factor in

experimental and the parts and the transistors is not perfectly measured by the Elvis

machine.

References

"Amplifier." Wikipedia. Wikimedia Foundation, n.d. Web. 01 Dec. 2015.

Adam, Mike. "Audio Engineering Society." AES San Francisco 2012 » Historical

Event H3:

Lee De Forest: The Man Who Invented the Amplifier. AES, n.d. Web. 01 Dec. 2015.