Lab practical assignments
ELT-S3-ELCL 1
bachelor Electrical Engineering
ELCL 1 Transistor circuits
Introduction
The transistor is a semiconductor for which the applications can be divided in two areas: the large
signal behavior (DC voltage and current) and the small signal behavior (AC voltage and current).
To find out how the transistor is operating basically, the best start is to build very basic circuits and
compare measurements with the calculations you could do on the basis of theory (usually Kirchoff KVL
and Thevenin’s equivalent covers 90% of the problem analysis).
Because transistors are semiconductors, where the production has a rather large tolerance, and also,
semiconductors have great temperature dependency, we will see that a pretty large difference may be
observed between the theoretical outcomes and the lab measurements.
ELCL1 consists of three assignments, which have to be finished in one block time and concluded with a
final report.
Goals
•
•
•
•
Investigate the voltage and current behavior of a BJT and a FET transistor.
Acknowledge measurement errors and do calculations to verify outcomes.
Investigate basic circuits with transistors to improve circuit analysis and practical skills.
Keep track of progress in a logbook and finally write a convincing report to confirm your knowledge.
Time schedule
3 x 2 hours Lab, 3 x 1 hour individual study, 2 hours report (per student).
Theory
Next knowledge of theory is supposed to be present:
Propedeutic phase Electrical Engineering:
• Network theory (circuit analysis with KVL, KCL, Thevenin, series/parallel, voltage and current
divider).
• Basic knowledge of components: resistor, power, diode, forward voltage, losses.
Main phase Electrical Engineering:
• Transistors , large signal properties and behavior, from: Floyd, Electronic Devices 10th ed.
(ConvCurVer).
Preparation
•
•
•
•
Know your way in the available website on #OnderwijsOnline Content. Know which chapters of the
Floyd book (10th edition) are applicable.
Have all the necessary datasheets ready on your laptop.
Take your own ADALM module and breadboard: it has to be in perfect order: all wires present and
reliable contacts. SCOPY has to be up-to-date (version 1.40).
Do your homework: finish all the preparatory questions before entering the lab. If you do not know
what is going on, then there is no sense in attending the lab sessions!!
Taking responsability and communicate
You will take up the assignments in a duo. You will make notes of the progress, as well as for
preparation time as the lab sessions themselves. These notes are the basis to communicate with the
lab lecturer, and they will be the basis of the report you will write.
Version 20220930
Page 1 of 15
dmn
Lab practical assignments
ELT-S3-ELCL 1
bachelor Electrical Engineering
The report is a presentation of your circuit analysis, calculations, observations, fault discussion and
conclusions. It shall answer the given questions and it must be readable without extra information on
your part.
How to….. the process of taking up the assignments
Tips and requirements……
The assignments will be prepared by reading the preparatory questions, and the weekly assignment as
a whole. Find out what you already know, and what will be the difficult parts to understand.
Find answers for the given preparatory questions.
Find datasheets that may give you information on certain components.
You will use components from the ADALP kit. If not available, you may obtain them from ARLE. Check
the availability beforehand, the ARLE desk is not open all day !
Build the circuit on the breadboard if possible. Certainly, make a start. Do not lose time on this in the
lab session.
Draw schematic diagrams in your logbook, so if you still have questions, the lab lecturer is able to give
you immediate comment on your understanding of the problem.
It is advised to have the working circuit checked by the lecturer, questions may arise, which will give
you an even better understanding of the outcomes of the measurements. If you skip this possibility of
reviewing your results, you may find out that you were on the wrong path at the time your report is
rejected. Best is, to take small steps and verify the outcome according to the questions and
assignments.
Report hand-in
•
•
The report will be handed in as PDF type. Details will be given in time.
The report is set up according to the standard guidelines. Ask about when you are not sure
about this. The basics are described in [ ELT-S3-ELCL Lab Electronics Description
20220705.pdf ]
Review of ELCL in full - getting your mark
The lab assignments are graded up to mark when:
• Lab has been attended
• A logbook can be presented if asked for
• Responsibility is shown in taking up the assignments
• The report is complete
• The report is handed in on time
Version 20220930
Page 2 of 15
dmn
Lab practical assignments
ELT-S3-ELCL 1
bachelor Electrical Engineering
Report tips and ideas
•
•
•
•
•
•
Find out for yourself what the most efficient way of report making is for you! Some like to work
with MS Word, some with OpenOffice, others go for Excel. You may even think of writing it on
paper in a neat way.
Take care not to lose too much time on presenting a ‘very beautiful form of writing a formula’,
make it readable yet professional convincing.
Do NOT make a mess of the sequence of elaboration. Make a clear start and (usually) line-byline work towards the end of an answer.
Circuit drawings, graphs and pictures must be readable and they must be reasonably sized. No
selfies or thumbnails, a guideline is 8 by 12 cm. (3 x 5 in.)
Every drawing, graph or picture MUST have a title, which describes it in a few words.
Reports with titles like “picture 1”, “setup of the breadboard”, “measurement 3” or the like WILL
BE REFUSED IMMEDIATELY.
Be aware that use of color is restricted, since printing on a black-and-white printer causes loss
of this information. Make use of arrows or text balloons
Textballoon to
indicate something
Get going with the breadboard
Shown is a typical component setup. Even with a few components it can already be messy and prone
to errors. Keep it clean and verify what you have built!!!
+V line
ADALM
extension
board
-V or
0 V line
Picture 1: working on the breadboard claims a systematic working method and accuracy. Do not use long wires
and close placement of components. Place components together when they have a common function, and
interconnect groups of functions with some longer wires. This gives you the opportunity to test separate functions
and it helps a great deal in fault-finding!!
Version 20220930
Page 3 of 15
dmn
Lab practical assignments
ELT-S3-ELCL 1
bachelor Electrical Engineering
Here is another example (visualised) of a possible setup:
Picture 2: example of a setup of the breadboard. At left, the decoupling capacitor is placed.
In this virtual presented setup, all the component leads are cut short, don’t do this, with longer wires it is
easier to bridge longer distances. However, these bare wires may short, so take care that components
are spaced on the board.
Note !!! With some breadboard, you need to connect the upper and lower long rails to get supplyvoltage
all over the boardlength !!
Connectivity tools
You must have breadboard intralinks in various colors and lenght.
Male - Female for connecting the ADALM signals,
Male – Male for interconnecting the breadboard strips.
It is handy to have about 4 croc-clip leads at hand.
Version 20220930
Page 4 of 15
dmn
Lab practical assignments
ELCL 1A
ELT-S3-ELCL 1
bachelor Electrical Engineering
Transistor, typical values and behavior
Preparation:
a. Read [Floyd: page 89, 90] Testing a diode.
b. Read [Floyd: page 182-188] BJT structure, operation, characteristics.
c. Read [Floyd: Chapt. 8.6, page 418, 421, 422, 435] E-MOSFET.
d. Have the ADALM and SCOPY ready with measuring leads.
e. Have the datasheets for 2N3904, 2N3906 and ZVN3310 available. Alternatives are: BC547, BC557
and 2N7000.
Questions
A1 What is the nominal VBE forward voltage?
A2 How many diode junctions can be found in a BJT?
A3 What would a nominal base current be for a small-signal BJT when IC = 50 mA and βF = 200 ?
1A1 Bipolar junction transistor
Measurements in the lab:
M1 Probing the leads
Take a 2N3904 or BC547, find out where the diodes are.
M1a Determine E-B-C leads.
M1b Write a conclusion that describes how you would determine that a BJT is faulty (broken) or not.
M2 Characteristic values, active region
R2
220Ω
Build the next circuit, which is derived from [Floyd – page
187, 188]:
Note that VBB = VCC
R1
100kΩ
T1
+ V1
10V
-
2N3904
BC547B
Schematic 1: bjt in active region
M2a
M2b
M2c
M2d
Measure the VCC and VBE voltage exactly.
Measure the collector current IC .
Calculate the basecurrent IB from measured values.
Calculate βF .
Version 20220930
Page 5 of 15
dmn
Lab practical assignments
ELT-S3-ELCL 1
bachelor Electrical Engineering
M3 Temperature dependency
Use the circuit of M2, but heat up the 2N3904 (BC547) with a cigarette lighter flame for 1 second at
time of next measurements:
M3a Measure the VBE voltage (exactly?).
M3b Measure the collector current I C .
M3c Describe the consequences for IB and IC in % when a BJT heats up.
M4 Characteristic values, saturation region
R4
470Ω
220Ω
Build the next circuit, which is derived from [Floyd – page
201]:
Note that VBB = VCC
R3
10kΩ
+ V2
10V
-
T2
2N3904
BC547B
Schematic 2: bjt in saturation region
M4a
M4b
M4c
M4d
Measure the VCC , VCE and VBE voltage exactly.
Measure the collector current I C .
Calculate the basecurrent IB from given and measured values (method: KVL with R3 and T2).
Calculate βsat for this circuit.
Okay, the transistor is conducting fully. Great! Maybe we forgot to check out what happened to R4 in
the meantime………….
M4e Findings on R4……
Version 20220930
Page 6 of 15
dmn
Lab practical assignments
ELT-S3-ELCL 1
bachelor Electrical Engineering
1A2 Field effect transistor – Nfet enhancement type
M5 Characteristic values, active region
Build the next circuit, which is derived from [Floyd
– page 437]:
The gate voltage is driven from a voltage divider. This
makes it easier to set the voltage.
Start with VR1 in the ‘middle’ position.
Moreover, a resistor is needed to inhibit ESD voltage on
the gate (R2).
Read [Floyd p.420] about handling precautions.
2N7000
Schematic 3: e-mosfet in active region
M5a Measure the VGS(th) voltage exactly by varying VR1. Look at Fig. 46 [Floyd p.418] to find out
what you want to do really.
M5b Set VGS so that the drain current ID is 15 ± 1 mA.
M5c Calculate the constant K from given and measured values. [Floyd p.418, equation 8-4]
M6 Characteristic values, on - region
Use the same circuit, from M5
We will now examine what happens when the gate is driven at a voltage, way beyond VGS(th) . The
induced channel between drain and source opens wide, and a lot of current may flow [Floyd p.418,
Fig.46]. The voltage VDS over the FET as voltagedivider, will go to a minimum.
In this situation, we may determine the on – resistance, RDS(on) .
This is a characteristic value for the FET as switching component.
M6a Set VGS to a value of 5 Volt. Measure VDS and IDS .
M6b Calculate RDS(on) .
M6c Calculate Pon of the FET.
Report:
Set up a pretty compact, but readable report of your answers and findings.
Version 20220930
Page 7 of 15
dmn
Lab practical assignments
ELCL 1B
ELT-S3-ELCL 1
bachelor Electrical Engineering
Current sources with BJT
“the BJT is a KVL machine”
Preparation:
a. Read [Floyd: page 241, 242] Voltage divider bias
b. Read [Floyd: page 244] Thevenizing
c. Read [Floyd: page 245, 246 ] BJT pnp type biasing, Fig. 15, example 4
d. Have the ADALM and SCOPY ready with measuring leads.
e. Have the datasheets for 2N3904, 2N3906 available. Alternatives are: BC547, BC557.
Questions
B1 What is the nominal VBE forward voltage?
B2 Describe a ‘stiff voltage divider’ ?
B3 Calculate the voltage divider from Schematic 4.
B4 Having read some stuff (a,b,c above), what is the prerequisite (what is needed) for all of the BJT to
work nicely? Think about ‘region’…..
1B1 Current sink
Measurements in the lab:
M1 Circuit with voltage divider
sink
Build the next circuit, which is derived from [Floyd –
page 242]:
R1
10kΩ
 IC
T1
RC is omitted, emphasizing the nature of a current sink.
+ V1
10V
-
2N3904
The load may be anything that is current-driven:
resistors, LEDs, transistors.
A true current-drive is independent of the applied
voltage.
BC547B
R2
1.5kΩ
Re
120Ω
Schematic 4: current sink with V-divider
Faultfinding:
On basis of Example 2 [Floyd page 242] the circuit may be recalculated if it appears not to be working.
Always start with verifying KVL in the divider – base loop (VBE + Vre – VR2 = 0).
M1a Measure the current for loads of 1kΩ, 470 Ω, 220Ω and 100Ω . Make a readable tabel of
measurements!! Is the BJT operating load-independent?
M1b Change the source voltage V1 to 8 Volt and measure the sink-current again. Why is the current
not independent from the source voltage?
Version 20220930
Page 8 of 15
dmn
Lab practical assignments
ELT-S3-ELCL 1
bachelor Electrical Engineering
M2 Circuit with diode stabilizer
Build the next circuit, which is derived from [Floyd – page 242]:
sink
R1
10kΩ
R2 is replaced by a red LED
 IC
T1
RC is omitted, emphasizing the nature of a current sink.
+ V1
10V
-
2N3904
D1
BC547B
Re
120Ω
LED_RED
Measure the current for a load of 220Ω.
Schematic 5: current sink with diode stabilizer
M2a Why has the sink current changed – compared to schematic 4? Measure the base voltage VB and
make a quick KVL calculation (see Example 2) to justify the measured value for IC .
M2b Change the source voltage V1 to 8 Volt, measure the sink-current. Is the current independent
from the source voltage? Also describe the reason for this.
Application Note for microprocessor control:
(switch on-off current sink)
To switch the current on and off, R1 may be connected to an output of a microprocessor. The value of R1 should
be adjusted so ID1 is about 1 mA.
Version 20220930
Page 9 of 15
dmn
Lab practical assignments
ELT-S3-ELCL 1
bachelor Electrical Engineering
1B2 Current source
Measurements in the lab:
Re
M3 Circuit with voltage divider
120Ω
R2
Build the next circuit, which is derived from [Floyd –
page 245, page 246 – example 4]:
Be sure to select a 2N3906 or BC557.
RC is omitted, emphasizing the nature of a current
source.
1.5kΩ
T1
2N3906
+ V1
10V
-
BC557B
R1
10kΩ
 IC
source
The load may be anything that is current-driven:
resistors, LEDs, transistors.
A true current-drive is independent of the applied
voltage.
Schematic 6: current source with V-divider
Faultfinding:
On basis of Example 4 [Floyd page 246] the circuit may be recalculated if it appears not to be working.
Always start with verifying KVL in the divider – base loop.
Also, Example 4 may give some ideas, although this is based on Thevenin approach.
M3a Use a load of 470Ω. Measure the source current IC. Now put another 120 Ω parallel over Re.
What happens…and was it expected?
Remove the parallel 120 Ω again.
M3b Use a load of 470Ω. Measure the source current IC. Now heat up the BJT with a flame. What is
happening, and was it expected?
To be sure of your conclusion, maybe you should measure VBE also.
Describe why the current is changing, and give the change in current in percentage.
Report:
Set up a pretty compact, but readable report of your answers and findings.
Version 20220930
Page 10 of 15
dmn
Lab practical assignments
ELCL 1C
ELT-S3-ELCL 1
bachelor Electrical Engineering
AC voltage amplifier with BJT
Goal:
The AC domain is not easy to understand, because the behavior of semiconductors is really different
from the DC domain. Yet, it is a good thing to look at one of those AC circuits, and get an idea what is
going on. Getting the amplifier to work is one thing that will structure your mind. So: build, build, think,
measure, play and be surprised.
Preparation:
a. Read [Floyd: page 241, 242] Voltage divider bias
b. Read [Floyd: page 274, 275, 276] Amplifier operation
c. Read [Floyd: page 280, 281, 282] Common emitter amplifier
d. Read [Floyd: page 288] Stability of voltage gain
d. Have the ADALM and SCOPY ready with measuring leads.
e. Have the datasheet for 2N3904 available. Alternative: BC547.
Questions
C1 Describe what is “Q-point” in a few sentences, and at what voltage would you expect the Q point
to be?
C2 Describe why the input and output sinewaves in Fig.2 [page 275] are anti-phase.
C3 Why are capacitors like C1, C2 needed in the amplifier circuit of Fig. 2 [page 275]?
C4 And what will the consequence be in the f-domain? What formula comes to mind?
Version 20220930
Page 11 of 15
dmn
Lab practical assignments
ELT-S3-ELCL 1
bachelor Electrical Engineering
1C1 AC amplifier with low voltage gain
Measurements in the lab:
M1 AC amplifier, low voltage gain
Build the next circuit, which is derived from [Floyd – page 275]:
Rc
1kΩ
R1
C2
22kΩ
out
VQ
T1
Rg
50Ω
V2
G + 1Vpk
- 1kHz
0°
in
C1
1µF
+ V1
15V
10 V
-
2N3904
BC547B
470nF
220 nF
R2
Re1
5.6kΩ
10 kΩ
33Ω
R3
33kΩ
Re2
470Ω
Schematic 7: AC amplifier with npn BJT
Design notes on schematic 7 circuit:
• Around T1, we recognise the standard current sink (voltage divider, transistor, Re). The load is
Rc. So, a Q point is set.
• Re is built of two Re, so the total value is half of Rc (1000 / 2 = 500). This ratio 2 makes life
easier for us, interpreting outcomes.
• Furthermore, capacitors are added to block the DC voltage, and let AC current through. R3 as a
load is needed to discharge C2 (otherwise you would see a slow DC voltage creeping down the
oscilloscope image; C2 would discharge over the 1MΩ resistance of the scope).
Building tips and Faultfinding:
Always start with the DC part. R1, R2, Re, Rc and T1. Check a valid Q point voltage.
On basis of Example 2 [Floyd page 242] the circuit may be recalculated if it appears not to be working.
Always start with verifying KVL in the divider – base loop (measure DCV !!).
Next add the capacitors. Observe polarity if applicable!!
Use the ADALM Wave1 output to give the ‘in’ signal.
Use SCOPY as oscilloscope to measure input and output values.
Usually, the input value is always displayed on Channel 1 as reference.
Version 20220930
Page 12 of 15
dmn
Lab practical assignments
ELT-S3-ELCL 1
bachelor Electrical Engineering
Measure input signal on Channel 1.
M1a Measure (Ch2) amplitude and phase of VE and VC (note: we are in AC domain, so forget DC !)
Explain the measurements. Determine the amplification factor A V =Vout/Vin
M1b Display Vin and Vout on the scope. Enlarge the input voltage, observe the output going into the
non-linear area. Draw a picture like Figure 3 in “Floyd” for your amplifier to explain what is happening.
M2 AC amplifier f-domain
Set the input voltage so, that the output is in the linear area, with a nice value ( 2.0 Vrms)
M2a Change the frequency up and down. Find the breakfrequency. Draw a Bodeplot.
M2b Which of the capacitors is the cause for this filter behavior?
Version 20220930
Page 13 of 15
dmn
Lab practical assignments
ELT-S3-ELCL 1
bachelor Electrical Engineering
1C2 AC amplifier with high voltage gain
Measurements in the lab:
M3 AC amplifier, high voltage gain
Adjust the circuit from sch. 7 with one capacitor, which is derived from [Floyd – page 281 and 289]:
Rc
1kΩ
R1
C2
22kΩ
VQ
T1
Rg
50Ω
V2
C1
in
1µF
+ V1
15V
- 10 V
2N3904
R3
BC547B
470nF
220
nF
G + 1Vpk
0.1 Vpk
out
33kΩ
Re1
R2
33Ω
5.6kΩ
10 kΩ
- 1kHz
0°
Re2
C3
470Ω
10µF
2.2µF
Schematic 8: AC amplifier with npn BJT, swamping emitter current
Design notes on schematic 8 circuit:
• Re will be bypassed with a capacitor. A full bypass would lead to a very high amplification,
which is not desirable (very small input levels would be needed).
• The partial bypass is called swamping ( the capacitor C3 acts like a ‘current swamp’ , it just gets
sucked up there). In the AC domain, Re2 may be forgotten….. that is….at what frequency?
Set the input to 0.1 Volt, 1 kHz.
Measure input signal on Channel 1.
M3a Measure (Ch2) amplitude and phase of VE and VC (note: we are in AC domain, so forget DC !)
Explain the measurements. Determine the amplification factor A V for the output.
M3b Display Vin and Vout on the scope. Enlarge the input voltage, observe the output going into the
non-linear area. Draw a picture like Figure 3 for your amplifier to explain what is happening.
M4 AC amplifier f-domain
Set the input voltage so, that the output is in the linear area, with a nice value ( 2.0 Vrms)
M4a Change the frequency up and down. Find the breakfrequency. Draw a Bodeplot.
M4b Which of the capacitors is the cause for this filter behavior?
Version 20220930
Page 14 of 15
dmn
Lab practical assignments
ELT-S3-ELCL 1
bachelor Electrical Engineering
1D End of ELCL1
Make a readable report of your analysis, calculations, measurements and other findings.
Pay attention to frontpage content, list of contents.
A guideline for the volume would be a total of 9 pages.
Deliver the report on time.
Sources:
https://www.hobbyelectronica.nl/product/dupont-male-male-breadboard-jumper-kabels-20cm/
https://www.beslist.nl/klussen/d0024073477/10_stks_Alligator_Clips_Doubleended_Meetsnoeren_Krokodil_Klem_50_cm.html
https://ftaelectronics.com/pair-of-heavy-duty-multimeter-voltmeter-test-probe-leads-1000v-10amax.html
Internet sites visited 190826 11:20
Schematic diagrams with
Multisim 13 - Circuit Design Suite , National Instruments
https://www.ni.com/nl-nl/support/downloads/software-products/download.multisim.html#452133
site visited 07 jul 22 15:50
EE-sim OASIS , Maxim Integrated
https://www.maximintegrated.com/en/design/design-tools/ee-sim-design-simulation-tool/oasis.html
site visited 07 jul 22 15:53
Schema / Afbeeldingen zijn vervaardigd door de auteur, tenzij bronvermelding is opgenomen.
In deze onderwijspublicatie is geen auteursrechtelijk beschermd werk opgenomen.
Version 20220930
Page 15 of 15
dmn