Download 1. Objective

EEE2146 Microelectronics Circuit Analysis and Design
Experiment MIC2
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MIC2: Investigation of Amplifier Parameters of a Common-Collector Amplifier
Total Percentage: 5% (From 40% Coursework Mark)
1. Objective
To investigate the voltage and current gains and input and output impedances with respect
to different operating conditions of a common-collector amplifier.
To determine the transistor parameters β, rπ and ro values at different biasing conditions.
2. Lists of Equipments and Components
Equipments
Qty. Components
Adjustable DC power supply
1
BJT 2N2222A
Function generator
1
Capacitor 10 µF (16 V)
Digital multimeter
1
Resistors (0.25 W) / Ω: 10, 20, 100,
200, 510, 4.7k, 5.1k, 10k, 6.2k
Dual-channel oscilloscope
1
Breadboard
1
Resistors (0.25 W) 1 kΩ
Qty.
1
2
Each one
2
3. Introduction
Figure 1, Figure 2 and Figure 3 shows a common-collector amplifier circuit, its smallsignal equivalent circuit and its equivalent circuit with Thevenin’s equivalent output circuit.


Because of the capacitors in the amplifier circuit, the voltage gain Av , current gain Ai , input


impedance Z i and output impedance Z o are functions of frequency, therefore, they are
  

vectors or complex numbers. The values of Av , Ai , Z i and Z o and their magnitudes can be
determined in experiment with the below equations.
 vo
 | vo |
Av  
| Av |
vi
| vi |


 | iL |
 iL
| Ai | 
Ai  
| ii |
ii

 | vi |
 vi
|Z i | 
Z i 
| ii |
ii

 
R
R



|v o |  L
| Avo | | vi |
v o   L Avo vi
| Z o  RL |
Z o  RL


The equation for Z o is derived according to Figure 3. Avo is unloaded voltage gain (RL = ∞),
 




Avo vi is equal to unloaded output voltage voo . | Z o  RL | (Z o  RL )( Z o  RL ) * , where


(Z o  RL ) * is the complex conjugate of (Z o  RL ) .
At mid-band frequencies, where the effect of the capacitors, i.e. reactance, is
  

negligible, Av , Ai , Z i and Z o are almost independent of frequency, i.e. they are close to real
numbers, Av, Ai, Ri and Ro. The equations to find the values of Av, Ai, Ri and Ro are given
below, where all the currents and voltages are almost independent of frequency.
v
v
i
RL
A v  o , Ai  L , R i  i , v o 
Avo vi
vi
ii
ii
Ro  RL
For further information, you can refer to lecture notes or any microelectronics books.
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EEE2146 Microelectronics Circuit Analysis and Design
Experiment MIC2
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Figure 1: A common-collector amplifier. The voltages, currents and impedances (except
VCC) have magnitude and phase. It is the same for those in Figure 2 and Figure 3.
Figure 2: Small-signal equivalent circuit of the CC amplifier
Figure 3: Equivalent circuit for the CE amplifier with Avo, Zi and Zo function of frequency
BJT pin layout:
General Guidelines (for Section 4, 5, 6 and 7):
- Plan to carry out your experiments systematically and efficiently (e.g. table for
recording data, measuring points, load connections).
- Use tables to record data & calculated values.
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EEE2146 Microelectronics Circuit Analysis and Design
Experiment MIC2
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-
-
There are many calculations in Section 5, hence you need to show deriving equation
work and describing calculation work (each repeated calculation work is not required
to be shown).
Use graphs to analyze recorded data and calculated values in Section 6, if necessary.
Tables and graphs are useful tools to observe the changes of variables or parameters
and to compare the same variable or parameter at different operating conditions.
Graph is more suitable than table when the total number of values involved is large.
You may use MS Excel or equivalent to plot graphs.
4. Experiments
Experimental setup, measurements and data collection:
(a) Construct the circuit as shown in Figure 1, where VCC = 12 V, R1 = 4.7 kΩ, R2 = 6.2 kΩ,
RE = 510 Ω, RS = 5.1 kΩ, RL = 10 Ω, C1 = C2 = 10 µF. Record voltages VCC, VB and VE.
(b) (With 0.2 V peak-to-peak (p-p) sine-wave for vs (RL = 10 Ω), record p-p voltages vi, vb,
ve, and vo at several frequencies from 100 Hz to 50 kHz (vi may be 9-23 mV & vo may be
7-19 mV since β may be 50-300. If vi is not within 15-23 mV, change vs. Record vs value.
Use this vs for the rest of experiments. Check vs time to time). Take at least 6 data points
with about equal space on log-scaled frequency-axis.
(c) With f = 10 kHz (vs = 0.2 V p-p), record p-p voltages vi and vo for RL = 10 Ω, 20 Ω, 100
Ω, 200 Ω, 1 kΩ, 10 kΩ and ∞.
(d) Change RE to 1 kΩ. Record voltages VCC, VB and VE .
(e) From Part (d), with f = 10 kHz (vs = 0.2 V p-p), record p-p voltages of vi and vo for RL =
10 Ω, 20 Ω, 100 Ω, 200 Ω, 1 kΩ and ∞.
5. Analysis
Calculate the below:
(a) β and rπ values from Part 4(a).
v v i i
v
(b) o , o , L , L and i values for each recorded frequency from Part 4(b).
v s vi i i i b
ii
v i i
v
(c) o , L , L & i values for each RL from Part 4(c).
vi i i i b
ii
(d) β and rπ values from Part 4(d).
v i
v
(e) o , L & i values for each RL from Part 4(e).
vi i i
ii
(f) The Ro value/s from Part 4(b).
(g) The Ro value/s from and Part 4(c).
(h) The Ro value/s from Part 4(e).
6. Discussions
Discuss on the below:
(a) The calculated results in Part 5(b). What is the trend on
vo vo i L i L
v
,
,
,
and i as
v s vi i i i b
ii
frequency changes
(b) The calculated results in Part 5(c). What is the trend on
vo vo i L i L
v
,
,
,
and i when
v s vi i i i b
ii
RL changes?
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EEE2146 Microelectronics Circuit Analysis and Design
Experiment MIC2
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(c) The calculated results in Part 5(c) and Part 5(e) by comparison. What can you see to
vo vo
i
,
and L when RE is doubled in Part 5(e) (i.e. compare at the same RL)?
v s vi
ii
(d) What happen to the Ro values from Part 5(f) and Part 5(h).
7. Report
Write a lab report consisting of experimental results, analysis, discussions and
conclusions. Please include necessary graph, table or chart. The report needs to be
HANDWRITTEN. Please include the standard lab report cover page.
8. Evaluation (Based on Rubrics as attached)
References: Lecture notes or any microelectronics books
Appendix: Log scale
~~ End of Lab sheets ~~
Prepared by: W.O. Siew, Nov 2013
Updated by: Zubaida Yusoff, Nov 2015
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