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EE 330 Analog Electronics Laboratory

Fall 2012

Instructor- Fei Wang

Experiment #7Design of a Common-Emitter Biasing

Circuit

Date Performed: 11/12/2012

Date Submitted: 11/30/2012

By

James Fitzgerald

Larry Harmon

Vinh Kim

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Objective

The purpose of experiment #7 is to learn how to design a common emitter amplifier

circuit by selecting the right resistors values and supply voltage.

List of Instruments

1) Breadboard

2) 4 Resistors: 1.66M , 5M , 4.7k , and 2k .

3) Alligator Clips4) Jumper wires

5) Power supply

6) 2N2222

7) 10 F

8) Oscilloscope

PreLab

A. Using the circuit below we calculated a resistance for Rl that would give a gain greater

than 2.

Vi

10F

Vcc

RB1

RB2

RL

RE

VO

4.7 k

2N2222

F igure 1Common Emitter Amplifier

Using these design considerations, select values and VCCso that the amplifier meets the

following specifications:

1. The circuit must provide an output voltage swing Vo of 10 volts peak to peak with no

distortion of the Vowaveshape. Distortion is defined as limiting of Vodue to the amplifier

operating the transistor near cutoff or saturation regions.

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2. It must provide this distortion-free amplification over the temperature range from 25C to

100C, and for any value beta from betaminto betamaxfor the 2N2222.

3.

It must provide a gain, Vo/Vi, of at least 2.

RL/RE = 4.7 k / 1.68 k = 2.78

4. The required VCCis 20 volts or less.

Are VCC= 15V

5. RL= 4.68 k PL= 6.32 mW I = 1.162mA

RE= 1.69 k PE= 2.325 mW I = 1.173 mA

RB1= 103.2k PB1= 1.389 mW I = .116 mA

RB2= 24.4 k PB2= .269 mW I = .105 mA

VCC= 15 volts

What peak-to-peak value of Viis needed to provide 10 volts p-p output?

Vip-p= 3.8 volts

Set-up

1. Set up the circuit of Figure 1 using your 2N2222 with your values of resistors and VCC.

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2. Set the input voltage, Vi, to the peak to peak value necessary to yield 10 Vp-pat Vo.

3) Connect the oscilloscope to view Vo and Vi simultaneously. If you do not observe an

undistorted Vo, it will be necessary to tweak the values of resistance in order to yield a

distortionless output.

In order to maximize our output results we set the output and get distortion to give a

better idea the area where our max input should be.

4) Record VBE, IC, VCE, gain, and the waveshapes of Vo and Vi on the same time axis.

Label the Vo and Vi waveshapes with their maxima and minima values. Place your

results in Table 1.

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Results

Complete Table 1 below.

Source BETA VBE(V) VCE(V) IC(mA) GAIN

Calculated

Using Specified

Beta (Use beta

in datasheet)

Bmin

35 0.7 V 7.49 V 1.164 2.78

Calculated Using

Measured Beta

(Use your results

from Lab 6)

249 0.7 V 7.503V 1.173 2.78

Measurements 100 0.7 V 7.56V 1.162 2.625

Questions

1. What are possible causes of differences between the calculated and experimental values of

VCE and IC?

2. What change in ICO(ICBO) did you anticipate over the temperature range of 25C to 100C?

3. Calculate the theoretical quiescent collector power dissipation of your transistor with beta =

betamin.

.

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4. How would the voltage gain of your amplifier be affected by reducing the 10 microfarad

capacitor? Explain.

Conclusion