Manual 3101

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Last modification - 6/8/12 Page - 1

University of Minnesota

Department of Electrical andComputer Engineering

EE 3101 Laboratory Manual

A Second Laboratory Course in

Electronics

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Introduction

You will find that this laboratory continues in the mode initiated in EE2002. It is intended to supplement the

Junior microelectronics course sequence and to familiarize you with instruments that will be used in later labs.

It is also intended to further develop your self-confidence in laboratory procedures and in drawing conclusions

from observations. As a consequence the instructions are very spare and assume you will be able to extractconclusions from each experiment and will relate parts of the total lab to each other without being explicitly

asked to do so.

Important Points

- Your grade in this course will depend principally on your in-lab work.

- You are expected to maintain a lab notebook. Your lab notebook must contain a running account of the

experiment. It is not intended to be a book into which you copy notes previously gathered on the back of an

envelope. It must however be legible and coherent. Write in such a way that another person could perform thesame experiment based on your account and this same person could understand the conclusions that you drew

from your data. It is not necessary to hide your mistakes. If you make a mistake in an entry simply draw a line

through that entry and start over - you will not be penalized for this.

- The lab notebook should have the following characteristics:

- It should be a bound notebook (spiral bound is ok).

- Lab entries should be dated, and should include:- Complete circuit diagrams.

- Explanation of circuit, methods, procedures, etc.

- All calculations for designs.- All measurements (including component values).

- All analysis and comparisons of data with theory.

- There are no formal lab homeworks or pre-labs in this course, but it will pay great dividends for you to make a

careful reading of the experiment description before arriving in the laboratory. You will also note that someparts of the "experiments" involve analytical work which can be better done elsewhere. Most problemsstudents have with this course are due to lack of preparation prior to coming to lab . If after readingthrough the lab and consulting the relevant section of your EE2001, EE2011, and EE3115 texts you do not

understand something, seek out either your TA or the faculty member in charge of the lab.

- MILESTONES. In each experiment there will be a few milestones. These are specific tasks which must beaccomplished and demonstrated to the TA or professor before going on to the next item. All milestones must be

completed or you will not pass the course. If the milestones are not completed by the end of the semester you

will receive an F for the course. While the milestones are not a part of the grade formula, delays in milestonecompletion will unavoidably delay the submission of your lab notebook with the corresponding grade penalty

Lab notebooks and lab write-ups will not be accepted if more than one milestone remains to be completedfor the corresponding lab.

- Grades. Grades will be determined from the following components of the course:

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Lab Notebooks - 30%Lab Practical Exams - 40% Take them seriously, they are forty minutes to one hour in

duration and account for a significant portion of your final

grade.Lab Reports- 30%

Lab notebooks will be collected up to three times during the semester. They will be due at 4:30 pm threeworking days after the scheduled completion date of a lab.

Lab write ups will be collected one week after scheduled completion of the lab.

You will be given a schedule during the first week of class which contains all lab practical exam dates and

notebook and lab write-up due dates.

- Late Penalties. The penalties for late notebooks or lab reports are as follows:

1 or 2 days late: 3% deducted from your FINAL SCORE.

3 or 4 days late - an additional 3% deducted from your FINAL SCORE.

and so on...

-You will receive a separate handout containing the specifications for the lab reports.

- Housekeeping Requirements.No food or drink to is be brought into the lab and most especially is not to be placed on the lab benches. At the

conclusion of each laboratory session, all cables, etc. are to be returned to the proper wire racks and any

borrowed equipment (there should be no borrowed equipment without the approval of the TA) returned to itsproper location. The only items on the lab bench when you leave should be the equipment normally found on

each bench. The TA will record a demerit against your record in his gradebook each time you fail to meet theabove standards. Four or more demerits at the end of the term after grades have been computed will result in

grade reduction of one level (A to A-, A- to B+, etc.). If for some reason, you find the lab bench does not meet

the above standards when you first come in, inform your TA immediately. You are still responsible for leaving

the lab bench neat when you leave.

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Experiment #1

Experiment #1: Introduction to Lab Procedures

and Review of PXI-Bus Instrumentation

Session 1

Introduction

The lab instructor will go over the procedures and

expectations for this course. He will then demonstratethe use of the computer controlled PXI-buss based

digital multimeter (DMM), oscilloscope, function

generator, and dc power supply. The review will be

cursory as it is expected that all students are familiarwith the equipment from EE2002 laboratory. The

student should then spend the rest of the lab period

trying out the equipment to become more familiar

with it.

Measurements

1. Connect the 6V dc supply terminals from the DC

power supply to the PXI-based DMM and the stand-

alone DMM as shown in Fig. 1-1. Vary the setting ofthe dc output and compare with the reading of the

DMMs. Be sure that the DMMs are set to read DC

volts.

Figure 1-1. Connection of dc power supply and digitalmultimeters (DMMs) for measuring dc voltage.

2. Repeat step #1 for the 0 to +20 supply and then the0 to -20 supply.

3. Display a 4 V peak-to-peak sinewave at a frequency

of 1 kHz on the oscilloscope. Connect the function

generator to the oscilloscope as shown in Fig.1- 2 to

obtain the display. Adjust both the vertical sensitivity(volts per division) and horizontal (time base)

sensitivity (seconds, milliseconds, microseconds) to

obtain a good display showing two or three cycles ofthe waveform.

Figure 1- 2. Connection of function generator tooscilloscope for displaying and measuring ac

waveforms. The connection of the DMM to measure

rms voltages is also shown.

4. Measure the amplitude of this ac waveform withthe DMM set on the ac voltage mode. Compare this

reading with the base-to-peak value you observe onthe oscilloscope.

The voltage measurements in steps #3 and step #4

should have different values. The DMM is calibratedto display the rms value of a sinewave which equals

0.707 of the base-to-peak value of a sinewave. Other

waveforms such as square waves and triangular waveswill have different rms-to-base-to-peak ratios as

measurements of step #5 will illustrate.

5, Repeat steps #3 and #4 with square waves and thentriangle waves.

A square wave has an rms value which is equal to the

base-to-peak value. A triangle wave has an rms valuevalue which is 0.578 of the base-to-peak value.

.

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6. Construct the circuit shown below in Fig. 1-3,

sometimes termed a voltage divider. Use a 4 V peak-to-peak 1 kHz sinewave for the input and measure the

output voltage with the oscilloscope and DMM.

The point of this step is to become familiar with usingthe protoboard to construct circuits and make

connections to sources and measurement instruments.

Examine the layout of the protoboard shown below inFig. 1-4 and note that a specific column of component

insertion holes are shorted together. Each individual

terminal of a component should be inserted into aseparate column as illustrated for a resistor unless it is

desired to have terminals shorted together.

Electrical connections to the function generator andoscilloscope are made via so-called BNC connector

terminals. The outer cases of these connectors are

directly connected to the ground (ground pin) of the

ac power plug. When these instruments are connectedto the AC power outlets, all of the instruments

grounds (BNC outer cases) are shorted together as

indicated in the figure. Any instrument that connectsto the AC power system is configured in this manner

(for reasons of safety). Thus it is not possible to

connect the oscilloscope so as to measure the voltageacross the 4 k resistor because the 1 k resistor

would then be shorted out.

Fig. 1-3. Voltage divider circuit and instrumentgrounding.

Fig. 1-4. Diagram of protoboard which is used to

construct circuits for laboratory measurements.

7. Replace the function generator with the 0-6V dcpower supply and repeat step #6.

8. Construct the circuit of Fig. 1-5. Set the DMM tomeasure dc currents. In this configuration the DMM

is being used to measure current.

Figure 1-5. Circuit arrangement for measuring

current through a resistor.

Compare the current measured by the DMM with the

current output indicated by the dc power supplydisplay. They should be the same.

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9. Construct the circuit of Fig. 1-6 and use it tomeasure the resistance of several of the resistors in

your lab kit. Make sure to use the proper set of

terminals on the DMM and set the DMM to measure

resistance.

Figure 1-6. Circuit for determining values of

resistors.Compare the reading of the DMM with the value of

resistance indicated by the color code on the resistor

body.

Experiment #2

RC Circuits

Sessions #2 and #3

Experiments

1. Construct a simple RC single time constant circuit

of the form shown.

Choose component values such as to make the time

constant about 0.1ms and determine the time constant

experimentally by observing resistor and capacitor

voltages when a square wave is applied to the inputport.

2. Determine the extent to which the output resistanceof the signal generator has affected the result of item

1.

3. Many applications require that a sharp pulse be

generated to mark the time at which a rapid change

occurs in a signal. Design a simple circuit based on

the work of the preceding items which will generate a

sharp spike whenever the square wave input changessign.

4. Investigate the magnitude and phase of the output

of the original RC circuit as the frequency of thedriving sinusoid is varied over a suitably wide range

Determine the frequency at which the magnitude is

down to 0.707 of its frequency-independent valueDetermine the frequency at which theoutput is phase

shifted by 45 degrees with respect to the input.

5. Return to your circuit of item 3 and repeat the

measurements of item 4.

_________________________________________

MILESTONE #2-1: Collect the results of items 1through 5 and show them to your instructor.

_________________________________________

6. Construct and test a circuit which generates a3+1sin( 2 f t ) V signal, with f = 10 kHz. Do notuse the signal generator dc offset for this purpose.

7. Design a circuit which will take the dc + ac signalgenerated by the circuit constructed in item 5 and pass

only its ac component along to a 100 k load resistor.

8. Design a circuit which will take the dc + ac signal

generated by the circuit constructed in item 6 and pass

only its dc component along to a 100 k load resistor.

Experiments

9. Design an RC high-pass section which will have a

corner frequency at about 200 Hz and a mid-band

Demonstration

The measurements in items #4 and #5 of the circuit

transfer function as a function of frequency (so-

called frequency response) were manual point-by-point measurements. Such repetitive measurements

can be automated with the PXI-based instruments

using a so-called LabView VI (virtual instrument).

Your lab instructor will deomonstrate the use of aVI entistled Bode Plotter which automates

frequency response measurements. This VI is found

in UofMnVI folder located in the Programs folder.

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input resistance of 10 k. Investigate the response on

the oscilloscope.

10. Design an RC low-pass section which will have a

corner frequency at about 2 kHz and a high-frequency

input resistance of 10 k. Investigate the response on

the oscilloscope.

11. Design an RC network having a mid-band inputresistance of 10 k and whose transmission falls by 3dB at 100 Hz and 10 kHz. Investigate the response.

12. Investigate the effect of your filter of item 11 on

square waves of various frequencies.

___________________________________________

MILESTONE #2-2: Demonstrate the circuit of item

11 to your instructor.___________________________________________

Experiment #3

Non-ideal Behavior of Electronic Components at

High Frequencies and Associated Measurement

Problems

Sessions #4 and #5

Introduction

Electrical measurements at high frequencies aresignificantly more difficult than are those at dc or low

frequencies. Shunt capacitance in interconnect cables

and in measuring instruments present unknown shunt

load impedances at the measurement terminals. Theseload impedances decrease (and thus the loading

increases) as the frequency increases. In this

experiment you will investigate the use of thecompensated attenuator or voltage probe as a means

of minimizing shunt capacitance problems.

Another effect observed at high frequencies isresonance in circuits containing both capacitance and

inductance. Resonance in series and parallel RLC

circuits will be examined.

Finally, at high frequencies, resistors and inductors

will manifest non-ideal behavior. The magnitude ofthe parasitic elements, particularly capacitance, which

are the sources of the non-ideal behavior, will be

measured and equivalent circuit representations forthe non-ideal behavior will be established.

Experiment

Shunt Capacitance and the RC Compensator

1. Measure the transfer function |Vo/Vi| of the circui

shown from 1 kHz to 1 MHz.

Use the experimental results to estimate the shunt

capacitance of the oscilloscope and interconnectingcable.

___________________________________________

MILESTONE #3-1: Demonstrate on the oscilloscope

how Vo changes as a function of frequency.___________________________________________

Resonance in RLC Circuits

2. Design a series RLC circuit (similar to that shown,

but with R = 0) which has a resonant frequency of 2

kHz.

Determine the resonant frequency and Q of your

circuit. Also determine the impedance Zin(jo) at the

resonant frequency.

___________________________________________

MILESTONE #3-2: Demonstrate that the circuit has

the intended resonant frequency and Q.

___________________________________________

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3. Now modify the circuit to make Q = 5. Drive the

resultant circuit with a 2 kHz square wave andobserve the current waveform. Compare the spectra of

the input voltage and current waveforms.

4. Determine the resonant frequency f0 of the circuit of

Item 2 for C values from 0.001uF to 0.1 F.

Determine the functional relationship between f0 andC.

5. Design a parallel resonant circuit (with R =

infinity) with a resonant frequency of 2 kHz.Determine the Q of your circuit. Now modify the

circuit (make R less than inifinite) to make Q = 5.

Measure the resonant frequency and Q of the circuit.

Also determine the admittance of the circuit at theresonant frequency.

___________________________________________

MILESTONE #3-3: Demonstrate, on theoscilloscope, your result for Item 5.

___________________________________________

Non-ideal Frequency Behavior of Passive

Components

6. Measure Vo/Vi as a function of frequency for this

circuit with R > 500 kand RL = 5 k

Measure well beyond the - 3 dB frequency. Use the

data to determine the parasitic capacitance in shunt

with the resistor R. IMPORTANT you must use a

10x probe to minimize the shunt capacitance of theoscilloscope!

___________________________________________

MILESTONE #3-4: Demonstrate, on theoscilloscope, the frequency response obtained for

Item 6.

___________________________________________

The circuit shown above is a typical equivalent circuit

used to account for the parasitic capacitance andresistance encountered in an inductor.

7. Use the circuit shown below to determine the

magnitude |Z(j)| of the impedance of the inductorused in item 2 from 100 Hz to 1 MHz. Use the data toestimate the L , Rw, and Cw of the equivalent circui

shown in item 2.

Quiz #1 - Exps. 1 - 3

Session #6

Experiment #4

Power Supplies

Sessions #7 and #8

Introduction

In this lab you will examine the basic building blocksof circuits that effect ac to dc conversion.

Experiment

Transformer and auto-transformer

Each station is supplied with a box containing a variac

(variable transformer) and a step-down transformer

These units are fused and it is easy to blow these

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fuses. Your TA will give you a short list of

procedures. If you follow them they will save you agood deal of trouble.

1. Measure the voltage across the secondary of the

transformer as a function of the primary voltage.

2. Connect this circuit and examine the diode andresistor voltage waveforms.

Capacitive Filtering

3. Place a suitable capacitor across the load (theresistor) of the previous item (observe the polarity).

Choose a capacitor that will give an RC time constantof about 15 ms. Again examine the waveforms.

4. Repeat item 3 using a different capacitor.

5. Repeat item 3 using a different load resistance.

___________________________________________

MILESTONE #4-1: Demonstrate and explain the

circuit of Item 5.

___________________________________________

6. Choose from the circuits of items 3,4 and 5 the one

that shows the minimum ripple (peak-to-peak) in the

load voltage and check the effect of reversing thepolarities of both the diode and the capacitor.

Full Wave Rectifier

7. Construct a circuit, driven from the center-tapped

secondary winding, that contains 2 diodes and 1resistor (the load) and is such that load current flows

on both half-cycles of the 60 Hz input.

(This type of circuit is known as "full-wave".)

8. Add to the circuit of Item 7 so as to make the load

voltage the best possible approximation to a DCvoltage.

Investigate the dependence of the resulting ripplevoltage on the load current.

9. Investigate the following power supply circui

(known as a "bridge" circuit).

Do not attach ground to point S in the circuit.

10. Add capacitive filtering to the circuit of Item 9.

___________________________________________

MILESTONE #4-2: Demonstrate the output voltageyou have achieved in the circuit of Item 10.

_____________________________________

Voltage Regulators

11. Investigate the power supply obtained byadding a Zener regulator to the output of either of the

full-wave circuits above.

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Design the regulator (and modify the full wave circuit,

if necessary) so that the load current may be variedfrom 0 to 20 ma while the load voltage varies by no

more than 1%.

12. Measure the output voltage of the 7805 voltageregulator over appropriate ranges of input voltage

and load current.

___________________________________________Milestone 4-3: Demonstrate the practical working

range of the 7805 voltage regulator.

___________________________________________

Experiment #5

Differential Amplifiers

Session #9

Introduction

The differential amplifier is one of the most important

and widely-used circuits in electrical engineering. Inthis experiment, you will design, construct, and test

such an amplifier.

Experiment

1. Design the differential amplifier shown so that Io

is less than 10 ma and R

e

less than 2 k, and the

output voltage swing Vc1 > 10 V peak-to-peak for a

differential input signal.

Use power supplies VCC = =15 V and VEE = -15 V.

The 2 K resistors are used to provide a DC path toground. Verify your dc design.

2. Measure the single-ended common mode gain at 1

kHz

Ac = 2Vo/(Vi1 + Vi2)

3. Measure the single-ended differential mode gain a1 kHz. Do not apply excessive differential voltages at

the input

Ad = Vo/(Vi1-Vi2)

.

Use the results of parts 2 and 3 to estimate thecommon mode rejection ratio CMRR.

4. Measure the output signal swing capability before

clipping occurs. Use differential input signals.

5. Replace the emitter resistor Re with the curren

source shown below.

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Design the current source so that the current I0

remains the same. Verify the correct dc operation of

the modified differential amplifier. NOTE: Yourinstructor may substitute another matched pair for the

3096 array. Consult your TA for more information.

6. Determine the common mode rejection ratio CMRRat 1 kHz for the modified differential amplifier.

___________________________________________

MILESTONE #5-1: Demonstrate that your finalcircuit functions well as a differential amplifier.

___________________________________________

Experiment #6

High-frequency Behavior of BJT's

Session #10 and #11

Introduction

The objective of this lab is to measure the components

in the hybrid- small-signal model of the BJT and toinvestigate the high frequency response of some

amplifier circuits using it. The diagram shows a

somewhat simplified model, which ignores thecomponent r ( sometimes shown in parallel with

C. Furthermore, the component ro will be ignored

in the early part of the experiment because it will be

shunted by a much smaller resistor.

Experiment

Hybrid- Model1. Use the following circuit to measure the inputresistance of the transistor at low frequencies, i.e. in a

frequency range where the device capacitances wil

have a negligible effect.

Notice that Ce and Cs are intended to be short circuits

atthe measurement frequency so choose them wisely.

Bias the transistor so that the collector current is about

1 ma. Noticethat RB shunts the input so it will have

to be chosen so as to have a negligible effect. In the

later stages of the experiment the combination of the

voltagesource and Rs will need to approximate a

current source so you may as well choose Rsappropriately at this time. Identify the model

parameters determined in this experiment.

__________________________________________

MILESTONE #6-1: Demonstrate your measurementof the BJT input resistance.

__________________________________________

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The current gain of the BJT shows single-pole

behavior with the frequency of the pole given by

1/fH=2r [C+ (1+gmRL) C]

where fH is the frequency at which the CURRENT

(not voltage!) gain has fallen 3 dB from its mid-bandvalue.

2. Measure the frequency fH using a value of RL just

large enough to enable you to measure the small

signal collector current.

You now have one equation in the 3 unknowns r,

C and C.

3. Now measure fHagain, this time with a capacitor

inserted between the collector and the base of the

transistor, i.e. in parallel with C.

The capacitor should be such as to make fH change by

approximately a factor of 2. Your TA will supply the

appropriate capacitors. Now you have a second

equation in the 3 unknown quantities, provided that

you know the value of the added capacitor.

4. Remove the capacitor added in the previous item

and increase the value of RL by about a factor of 10.

(But it certainly must not be greater than about 1K.)

Again it should be such as to change fH by a factor of

about 2, compared to the result obtained in item 2.

5. Solve the 3 equations that result from the

measurements (items 2,3 and 4) for the 3 unknownquantities and, using the result of item 1, also

determine the value of rx.

Cascode Amplifier

The circuit used in the foregoing was basically a

common-emitter amplifier. You have observed theconnection between its midband gain and its

bandwidth, the latter decreasing as the former

increases. A circuit which allows greater bandwidthat a given gain is the cascode which is a common

emitter / common base pair (CE-CB)

6. Build a cascode amplifier using the figure below asa guide. Measure the gain and bandwidth of this

circuit and compare with the values obtained earlier

in this lab. Use a VCCof at least 10v and design for

a collector current of about 1 ma.___________________________________________

MILESTONE #6-2: Demonstrate that your cascode

amplifier has a reasonable dynamic range and explainhow the gain and bandwidth were measured.

___________________________________________

7. Measure the gain and bandwidth of a CC-CB pair

for comparison with previous results.

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___________________________________________

MILESTONE #6-3: Demonstrate that your CC-CBamplifier has a reasonable dynamic range.

___________________________________________

8. Make a set of measurements to compare the CC-CBpair with the 2 amplifiers investigated in the previous

items.

Quiz #2 - Exps. 1-6

Session #12

Experiment #7

Operational Amplifiers

Sessions #13 and #14

Introduction

This lab will investigate some of the non idealoperating behavior of the 741 opamp, with particular

emphasis on frequency response characteristics. In

addition, opamp use in the design of active filters willbe studied. The op amps are to be operated from 15

V supplies, unless otherwise stated.

Experiment

Operating Characteristics

1. Construct an inverting amplifier with a voltagegain of 5 and investigate the linearity and dynamic

range of its output as a function of op amp supply

voltages for an input sinusoidal signal at 1 kHz. Usethe oscilloscope for this purpose.

2. Measure the voltage gain vs. frequency for an

amplifier having gains of 1,5, 20 and 40.

In particular, determine for each case the frequency at

which the gain falls to 0.707 of the low frequencyvalue.

3. Determine the slew rate of the op amp using a

unity-gain voltage follower with a square wave inputsignal vs(t) at 50 kHz.

Also investigate the effect of the slew rate on

sinusoidal input signals of various amplitudes andfrequencies. Does the relationship between the slew

rate, the signal frequency, and the maximum

undistorted output amplitude agree with theory?___________________________________________

MILESTONE #7-1: Demonstrate the slew rate

limitation effect to your instructor or TA.___________________________________________

Active Filters

4. Construct the circuit shown below and determine

its transfer characteristic and its cutoff frequency f3dB.

What filtering function does this circuit implement?

Compare the low frequency gain and the cutoff

frequency with the theoretical value of:

Ao = - R2 / R1

3dB = 1/CR2 .___________________________________________

MILESTONE #7-2: Demonstrate the transfer

characteristic of the active filter and its cutofffrequency. PSPICE DEMO: Bring the results of a

PSPICE simulation of the amplifier (an AC sweep)

and demonstrate that the simulation reproduces whatyou have just demonstrated on the lab bench

___________________________________________

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5. Construct the circuit shown below and determine

its transfer characteristic and its cutoff frequency f3dB.

What filtering function does this circuit implement?Compare the cutoff frequency with the theoretical

value of:

3dB = 1/(1.414RC) .

Compare the roll off (in dB/decade) of this filter withthat of Item 4.

6. Construct the circuit shown below. Determine its

transfer characteristic and the center frequency fo atwhich the gain is a maximum.

What filtering function does this circuit implement?

Compare the mid band gain H (the gain at ), the

center frequency , and the bandwidth with the

theoretical values of:

H = 1

=1 + R/Rr

2RC

= 1/RC .

Investigate the effect on the parameterQ = of varying R and compare with theory.

___________________________________________

MILESTONE #7-3: Demonstrate the transfercharacteristic of the active filter of Item 6.

___________________________________________

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Manual 3101