Experiment 8

EE 214 Electronic Circuits Laboratory
Spring 2015
EXPERIMENT VIII
BIPOLAR JUNCTION TRANSISTOR CHARACTERISTICS
Objectives
The input and the output characteristics of bipolar junction transistors (BJT) will be investigated.
Preliminary Work
1. Read the Notes on Transistors.
2. Recalling that a BJT consists of two pn junctions, explain how you can check whether the transistor is
defective or not by using the diode-test utility of the multimeter. Do the same methods give an idea
whether the transistor is pnp or npn? How?
3. In the laboratory, the bipolar junction transistors C557B and C547B will be used. Find the related
datasheets and read the technical specifications. Outline their maximum ratings and the range for the
parameter 𝛽. You are recommended to read “3.9 Transistor Specification Sheet” section of the book
Electronic Devices and Circuit Theory by Robert Boylestad and Louis Nashelsky in order to learn how to
read transistor datasheets.
4. a. The circuit given in Figure 1 will be used to display the input characteristics 𝐼𝐵 − 𝑉𝐵𝐸 of an npn
transistor. Show the probe connections to obtain the input characteristics using oscilloscope. You may
assume that the frequency is low enough so that the function generator gives floating output. Draw
roughly the curve you expect to see on the oscilloscope screen. Comment on the functions of 𝑅𝑏 and
D. Note that 𝑅𝑐 is used for current limitation.
Figure 1
b. Modify the circuit given in Figure 1 to obtain the input characteristics of a pnp transistor.
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EE 214 Electronic Circuits Laboratory
Spring 2015
5. a. The circuit of Figure 2 will be used to display the common base output characteristics 𝐼𝐶 − 𝑉𝐶𝐵 of
an npn transistor for different emitter currents, 𝐼𝐸 . Show the probe connections to obtain the output
characteristics using oscilloscope when low-frequency assumption is still valid. Draw roughly the curve
you expect to see on the screen. Comment on the functions of 𝑅𝑐, 𝐷 and 𝑅 𝑒2. Note that 𝑅𝑒1 is used
for current limitation.
Figure 2
b. Modify the circuit given in Figure 2 to obtain the common base output characteristics of a pnp
transistor.
6. a. The circuit of Figure 3 will be used to display the common emitter output characteristics,
𝐼𝐶 − 𝑉𝐶𝐸 , of an npn transistor. Show the probe connections to obtain the output characteristics using
oscilloscope when low-frequency assumption is still valid. Draw roughly the curve you expect to see
on the screen. Comment on the functions of 𝑅𝑏2 and D. Note that Rb1 and 𝑅𝑐 are used for current
limitation.
Figure 3
b. Modify the circuit given in Figure 3 to obtain the common emitter output characteristics of a pnp
transistor.
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EE 214 Electronic Circuits Laboratory
Spring 2015
7. Simulation Work (MUST)
a. Simulate the circuit in Figure 1 to obtain 𝐼𝐵 − 𝑉𝐵𝐸 of an npn transistor using the transient option
of the simulation command. Note that parametric plot is possible in LTSpice, so you can obtain 𝐼 −
𝑉 characteristics of any circuit element. For further information, check their website.
b. Simulate the circuit in Figure 4 to obtain 𝐼𝐵 − 𝑉𝐵𝐸 of an npn transistor. Use DC Sweep option of
the simulation command to sweep the voltage of a DC supply you will use as 6 V supply in the figure.
You may utilise For Range values in Figure 5 for the simulation.
c. Simulate the circuit in Figure 6 to obtain common base output characteristics, 𝐼𝐶 − 𝑉𝐶𝐵 , of an npn
transistor. Use DC Sweep to sweep voltages of two DC supplies and utilise For Range values in Figure
7 for the simulation. Use 6V supply of Figure 6 as the first source to sweep in the simulation and
25V supply of figure as the second source to sweep.
d. Simulate the circuit in Figure 8 to obtain common emitter output characteristics, 𝐼𝐶 − 𝑉𝐶𝐸, of an
npn transistor. Use DC Sweep to sweep voltages of two DC supplies and utilise For Range values in
Figure 9 for the simulation.
Equipment List
Oscilloscope, Function Generator, Multimeter, DC Supply, Computer
Diode (1N 4001),
Resistors (3 x 1 kΩ, 10 kΩ)
Transistors (C557B, C547B),
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EE 214 Electronic Circuits Laboratory
Spring 2015
Experimental Procedure
1. Check whether the transistors C547B and C557B are defective or not; pnp or npn using the diode test.
2. a. Set up the circuit of Figure 1 to display the input characteristics of an npn transistor C547B and draw
the observed result. Use 𝑅 𝑏 = 1𝑘𝜴, 𝑅𝑐 = 1𝑘𝜴, D: 1N4001, 12V for the DC supply and the grounded
signal generator at frequency 100Hz for vi. Remember that our oscilloscope does not have add-inverse
utility at X-Y mode. (Hint: At 100Hz the signal generator behaves as floating signal generator)
b. Instead of using function generator and diode pair in order to sweep 𝑉𝐵𝐸 voltage, a DC supply can
be used to sweep voltage with the help of HPVEE. Note that the DC supply in the laboratory provides
three independent outputs. After setting up the circuit of Figure 4, follow the steps given to construct
the HPVEE program.
Figure 4
+6V output of the power supply will be used to sweep the base voltage i n order to obtain the
𝐼𝐵 𝑣𝑠. 𝑉𝐵𝐸 characteristics of a BJT. In addition, +25V output of the power supply will be used to set the
collector voltage to +9V. Both sources will be used under PC control. For this purpose,
1. Set up the circuit in Figure 4.
2. Turn on the computer.
3. Run the “Agilent Connection Expert” program which has a shortcut on the desktop.
4. Run the “Agilent-VEE” program which has also a shortcut on the desktop.
5. From the menu bar select I/O → Instrument Manager. Click on HP E3631A and place the Plug&Play
Driver in the work area. This driver will control the +6V (V B) output of the power supply.
6. Double click on the title bar of the driver, a properties window will open at the left of the screen;
enter “VB” as the title.
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EE 214 Electronic Circuits Laboratory
Spring 2015
7. Double click on the highlighted transaction bar of the HP E3631A Plug&Play Driver. Now you get
the dialog box which you will use to perform the desired task with the instrument. Double click on
“Set voltage” under “Source” folder. Select instrument1 which controls the +6V output of the
power supply.
8. Our aim is to sweep the output of the power supply. Therefore, we will create a control terminal
through which we enter the value of the desired output voltage. In order to create an input control
terminal, click on “Configuration” and then on “variable” and “Create input termin al” under
“voltage”. Click on OK. Now, an input terminal (voltage) is created on the driver.
9. Select Flow → Repeat → For Range from the menu bar and place it to the left of V B. Connect the
output pin of the For Range object to the volt input of HP E3631A Driver. Set up the values so that
the source supplies voltage starting from 0.1V up to 2V with 0.1V steps.
10. Another HP E3631A Plug&Play Driver will be used to control the +25V (V C) output of the power
supply. Place another HP E3631A Plug&Play Driver in the work area by selecting I/O → Instrument
Manager → HP E3631A → Plug&Play Driver.
11. Double click on the title bar of the driver, a menu will appear at the left of the screen, enter “VC”
as the title.
12. Double click on the highlighted transaction bar of the HP E3631A Plug&Play Driver. Now you get
the dialog box which you will use to perform the desired task with the instrument. Double click on
“Set voltage” under “Source” folder. Select instrument2 which controls the +25V output of the
power supply. Use the box right of the instrument box and set the voltage to 9V.
13. From the menu bar select I/O → Instrument Manager. Click on HP34401A and then on Plug&Play
Driver. Place the driver in the work area and name it “IB”. This driver will control the multimeter
in current measuring mode in order to measure I B.
14. Double click on the highlighted transaction bar of the HP34401A Plug&Play Driver. Under High Level
Control, select Measure → Take Measurement. Select DC current under function. Enter “3e-02”
under range and enter “1e-04” under resolution. Click on Configuration and choose the Create
output terminal option under reading. Click on OK.
15. Select Flow → Delay. Place the “Delay” object in the work area. Set the delay to 0.5 sec.
16. Connect the output pin of the For Range object controlling VB to the sequence input pin of the
Delay object.
17. Connect the sequence output pin of the Delay object to the sequence input of the HP 34401A
Plug&Play Driver.
18. Select Device→ Formula. Place the Formula object in the work area. Click on the upper left corner
of the Formula object and add input terminal which appears as B. Write the the equation of 𝐴 −
(1000 ∗ 𝐵) inside the box, where 𝐵 is the output of multimeter and corresponds to I B current and
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EE 214 Electronic Circuits Laboratory
Spring 2015
A is the 𝑉𝑖𝑛 voltage. 𝐴 − (1000 ∗ 𝐵) corresponds to V BE voltage.
19. Connect the output of the For Range object to the input A of the Formula object and connect the
reading output of the HP 34401A Plug& Play Driver to the input B of the Formula object.
20. Select Display → X vs. Y Plot. Place the X vs. Y Plot object in the work area. Name it “IB vs. VBE”.
21. Connect the reading output of the HP 34401A Plug&Play Driver to the y input of the X vs. Y Plot
object and connect the result output of the formula to the x input of the X vs. Y object.
22. Click on the upper left corner of title bar (there is a bar at the upper left corner) click to add terminal
and choose control input as autoscale. Then, an autoscale button will appear at the X vs. Y plot
object. Connect the sequence-out pin of the for range object to the autoscale input of the X vs. Y
plot object.
23. Your arrangement should look like as in Figure 5.
0.1
Figure 5
25. Run the program and observe the characteristics on the “X vs. Y Plot” object.
26. Plot the graph you observed to the report sheet and indicate the point where current will start.
How we call that voltage value?
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EE 214 Electronic Circuits Laboratory
Spring 2015
3. a. Set up the circuit of Figure 6 in order to display the common base output characteristics, 𝐼𝐶 − 𝑉𝐶𝐵 ,
of an npn transistor, C547B. Then construct the HPVEE program given at Figure 7 and sketch the
characteristics. Why we observe I C current while V CB is negative?
Figure 6
Figure 7
b. Modify the circuit to display the output characteristics of a pnp transistor, C557B. Then, repeat Part
3.a.
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EE 214 Electronic Circuits Laboratory
Spring 2015
4. a. Set up the circuit of Figure 8 in order to display the common emitter output characteristics, 𝐼𝐶 − 𝑉𝐶𝐸,
of an npn transistor, C547B. Construct the HPVEE program given at Figure 9 and sketch the
characteristics. Why is there a slope at the forward active region of BJT? What is “Early Voltage”? Show
it on your plot. (Its value is not important; just show how you can find it graphically)
Figure 8
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Figure 9
b. Modify the circuit of Part 4.a to display the output characteristics of a pnp transistor C557B. Then,
repeat Part 4.a.
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EE 214 Electronic Circuits Laboratory
Spring 2015
Student 1 :
Student 2 :
Assistant :
Group:
Date:
EXPERIMENT VIII
BIPOLAR JUNCTION TRANSISTOR CHARACTERISTICS
Experimental Results
1.
2.
a.
b.
Comments:
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EE 214 Electronic Circuits Laboratory
Spring 2015
3. a.
b.
Comments:
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EE 214 Electronic Circuits Laboratory
Spring 2015
4. a.
b.
Comments:
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EE 214 Electronic Circuits Laboratory
Spring 2015
Conclusion
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