EE3101 Lab Manual 2013 UMN

Last modification - 8/31/13 Page - 1

University of Minnesota

Department of Electrical and

Computer Engineering

EE 3101 Laboratory Manual

A Second Laboratory Course in

Electronics


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 extract

conclusions 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 the

same 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 some

parts of the "experiments" involve analytical work which can be better done elsewhere. Most problems

students have with this course are due to lack of preparation prior to coming to lab. If after reading

through 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 be

accomplished 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 milestone

completion 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 completed

for the corresponding lab.

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


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 three

working 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 its

proper 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 the

above 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.


Experiment Schedule

Week # Experiment Title

1 No labs in Week #1

2 Frequency Response and Filters

3 Frequency Response and Filters

4 Parasitic Capacitance and High Frequency Measurement Problems

5 Lab Quiz #1

6 Power Supplies

7 Power Supplies

8 Differential Amplifiers

9 High Frequency Behavior of MOSFETs

10 High Frequency Behavior of MOSFETs

11 Lab Quiz #2

12 Op Amps

13 Op Amps

14 Feedback Amplifiers

15 Feedback Amplifiers


Experiment #1

Frequency Response and Filters

Sessions #1 and #2

The behavior of a circuit’s transfer function as the

input frequency is changed (i.e. the circuit’s frequency

response) is important in many situations. This

experiment explores how frequency response

measurements are made and investigates the behavior

of several important filter circuits.

Experiments

1. Design and construct the R-C shown below which

implements a low pass filter. The corner frequency

should be 2 kHz and the high frequency input

impedance should be 10 kΩ. Measure the magnitude

and phase of the output of the circuit as the frequency

of the driving sinusoid is varied over a suitably wide

range. Determine the frequency at which the

magnitude is down to 0.707 of its frequency-

independent value. Determine the frequency at which

the output is phase shifted by 45 degrees with respect

to the input.

Figure 1-1. RC low pass filter.

2. Interchange the position of the resistor and

capacitor in the circuit of Fig. 1-1 (thus implementing

a high pass filter) while keeping the component values

unchanged. Repeat the measurements of step #1.

Determine the frequency at which the magnitude is

down to 0.707 of its frequency-independent value.

Determine the frequency at which the output is phase

shifted by 45 degrees with respect to the input.

___________________________________________

MILESTONE #1-1: Collect the results of items 1 and

2 and show them to your instructor.

___________________________________________

Filter circuits utilizing inductors, capacitors, and

resistors have much better characteristics than R-C

based filters. A prototype R-L-C low pass filter is

shown in Fig. 1-2. The resistance Rw represents the

winding resistance of the inductor.

Figure 1-2. R-L-C low pass filter.

3. Using your 10 mH inductor design and construct

the prototype low pass filter of Fig. 1-2. The 3 db

cutoff frequency is to be 2 kHz which is also the

resonant frequency of the circuit. Measure the

frequency response of this filter. Use the results to

determine the resonant frequency and the Q of the

circuit.

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).Two identical PXI-based setups will be

available on a dedicated bench in the laboratory

where the LCR meter is also located. Your lab

instructor will demonstrate the use of a VI entitled

Bode Plotter which automates frequency response

measurements. This VI is found in UofMnVI

folder located in the Programs folder.


The R-L-C prototype filter of Fig. 1-2 is not a

satisfactory low pass filter because of the large

resonant peak at 2 kHz. That peak must be removed in

order to have a decent filter.

4. Put a resistor in series with the inductor as shown in

Fig. 1-3. Choose the value of R1 so that the circuit Q

= 1. Measure the frequency response from 200 HZ to

20 kHz. Compare the response of this circuit with that

of the R-C low pass of Fig. 1-1 by plotting both

magnitude frequency responses on the same graph.

Figure 1-3. R-L-C low pass filter. R1 is chosen to

make the Q = 1.

5. Investigate the effect of your lowpass filter of step

#4 on square waves of various frequencies in the

range of 200 Hz to 2 kHz.

6. Design and construct the series RLC circuit shown

in Fig. 1-4 (which implements a bandpass filter) to

have a resonant frequency fo = 5 KHz and a Q = 5.

Measure the magnitude and phase of the transfer

function Vo/Vi over a wide enough frequency range

(0.1fo< f < 10fo) so that the complete frequency-

dependent behavior of the transfer function is

determined. Use your 10 mH inductor.

Fig. 1-4. R-L-C bandpass filter

7. The parallel resonant circuit of Fig. 1-5 implements

a bandreject filter. Design and construct this circuit so

that the rejection frequency (the resonant frequency of

the circuit) is 5 kHz and the circuit Q = 5. Measure the

amplitude frequency response from 500 Hz to 50 kHz

RLC Bandpass Filter Transfer Function

Vout

Vin =

w /(woQ)

{1- (w /wo)2}2 + {w /wo}

2Q-2 ;

= 2πf

<) (Vout/Vin) = tan-1

Qwo

w-

w

wo

ì í î

ü ý þ

é

ë ê

ù

û ú

resonant frequency fo = 1

2π LC ;

Q = 2πfoL

R ; R = Rw + R1 in Fig. 2-4.

Trasnsfer Function of RLC Low Pass

Filter

Vout

Vin =

1

{1- (w /wo)2}2 + {w /wo}

2Q-2 ;

= 2πf


1

Q w /wo -wo /w( )

ì í î

ü ý þ


2π LC ;

Q = 2πfoL

R ; R = Rw in Fig. 2-2.

R = Rw + R1 in Fig. 2-3.


Figure 1-5. Bandreject filter.

___________________________________________

MILESTONE #1-2: Demonstrate the circuit of item

7 to your instructor.

___________________________________________

Experiment #2

Parasitic Capacitance and High Frequency

Measurement Problems

Session #3

Shunt Capacitance and the RC Compensator

Shunt capacitance in interconnect cables and

measuring instruments present unknown shunt

impedances at the measurement terminals. Figure 2-1

illustrates the potential problem. If Rm >> Rth and the

effect of Cm were neglected, then it would be

expected that Vout = Vin. However at high

frequencies neglecting the effect of Cm could result in

serious measurement errors because the impedance of

Cm could be much less than Rm.

1. Drive the circuit of Fig. 2-1 with a 2 V p-p 20 kHz

square wave and compare the rise and fall times of

Vin and Vout. Use a 100 kΩ resistor for Rth and

connect Vin to channel #1 of your oscilloscope and

Vout to channel #2 of the scope. Use a two or three

foot coax cable with a banana plug adapter to connect

the scope to the circuit.

Use the experimental results to estimate the shunt

capacitance of the oscilloscope-cable combination.

The value of Rm for oscilloscopes is 1 MΩ.

Figure 2-1. Circuit for demonstrating the effect of

measuring instrument (oscilloscope) input

capacitance.

The use of a voltage probe consisting of the parallel

combination of a resistor Rp and a variable

capacitance Cp as shown in Fig. 2-2 forms a

compensated attenuator circuit offers a solution to the

shunt capacitance problem. When the attenuator is

properly compensated (RpCp = RmCm) the effective

impedance at the Vin terminals presented by the

attenuator circuit is a resistance of Rin = Rm + Rp and

a capacitance Cin = CmRp/( Rm + Rp), For a

conventional X10 voltage probe, Rin = 10 MΩ and

Cin = Cm/10.and the transfer function Vout/Vin = 0.1

independent of frequency.

RLC Bandreject Filter Transfer Function

Vout

Vin =

1- (w /(wo)2

{1- (w /wo)2}2 + {w /wo}

2Q-2 ;

= 2πf


1

Qwo

w-

w

wo

ì í î

ü ý þ

ì

í

ï ï

î

ï ï

ü

ý

ï ï

þ

ï ï


2π LC ;

Q = 2πfoL

R ; R >> then inductor winding

resistance in circuit of Fig. 1-5.


Figure 2-2. Compensated attenuator.

Figure 2-3. Compensation of a voltage probe.

The waveforms are Vout of the attenuator

when Vin is a square wave.

2. Obtain a X10 voltage probe from wire rack in the

lab and adjust Cp until you achieve compensation.

Your oscilloscope has a pair of terminals which has a

1V p-p 1 kHz square wave available for doing the

compensation. Use your compensated probe in place

of the two to three foot long coax cable with the

banana plug adapter to repeat the measurements of

Step #1.

What is the measured rise/fall time of Vin and the

shunt capacitance of the X10 probe?

___________________________________________

MILESTONE #2-1: Demonstrate the use of the X10

voltage probe to your lab instructor and how you

estimated the Cin of the probe.

_________________________________________

Non-ideal Frequency Behavior of Passive

Components

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

circuit with R ≈ 500 k and RL = 5 k

Figure 2-4. Measuring circuit for estimating the

parasitic capacitance in shunt with a large resistor.

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 capacitance in parallel with

RL.

The circuit shown in Fig. 325 is an equivalent circuit

used to account for the parasitic capacitance and

resistance found in real inductors.

Figure 2-5. Equivalent circuit of a physically

realizable inductor

4. Use the circuit shown below to determine the

magnitude |Z(j)| of the impedance of the inductor

from 100 Hz to 1 MHz. Use the 100 mH inductor in

the your lab kit.


Figure 2-6. Measurement circuit for characterizing an

inductor.

Use the data to estimate the L , Rw, and Cw of the

equivalent circuit shown in Fig. 2-5. What is the self-

resonant frequency of the inductor and what is

inductor Q at this frequency.

Quiz #1 - Exps. 1 - 2

Session #4

Experiment #3

Power Supplies

Sessions #5 and #6

Introduction

In this lab you will examine the basic building blocks

of circuits used in ac to dc conversion and the

construction of DC power supplies.

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

fuses. Your TA will give you a short list of

procedures. If you follow them they will save you a

good 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 and

resistor voltage waveforms.

Note that the diode is ungounded so a single

oscilloscope channel cannot be directly connected

across the diode. Use both scope channels to

implement a pseudo-differential measurement.

Consult your lab instructor if you are unsure about

how to do this.

Capacitive Filtering

3. Place a suitable capacitor across the load (the

resistor) of the previous item (observe the polarity).

Choose a capacitor that will give an RC time constant

of 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 #3-1: 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 the

polarities of both the diode and the capacitor.

When the diode in the half-wave rectifier is reversed,

the capacitor must also be reversed because you most

likely used an elecrolytic capacitor which has a


polarity designation. If electrolytic capacitors have a

dc voltage voltage across them in the wrong direction,

they may fail, sometimes even explode.

Full Wave Rectifier

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

secondary winding, that contains 2 diodes and 1

resistor (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 DC

voltage.

Investigate the dependence of the resulting ripple

voltage on the load current.

9. Investigate the following power supply circuit

(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 #3-2: Demonstrate the output voltage

you have achieved in the circuit of Item 10.

_____________________________________

Voltage Regulators

11. Investigate the “power supply“ obtained by

adding a Zener regulator to the output of either of the

full-wave circuits above.

Design the regulator (and modify the full wave circuit,

if necessary) so that the load current may be varied

from 0 to 20 ma while the load voltage varies by no

more than 1%.

12. Measure the output voltage of the 7805 voltage

regulator over appropriate ranges of input voltage

and load current.

___________________________________________

Milestone 3-3: Demonstrate the practical working

range of the 7805 voltage regulator.

___________________________________________

Experiment #5

Differential Amplifiers

Session #7

Introduction

The differential amplifier is one of the most important

and widely-used circuits in electrical engineering. In

this 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 Re 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 to

ground. 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 at

1 kHz. Do not apply excessive differential voltages at

the input

Ad = Vo/(Vi1-Vi2)

.

Use the results of parts 2 and 3 to estimate the

common 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 current

source shown below.

Design the current source so that the current I0

remains the same. Verify the correct dc operation of

the modified differential amplifier. NOTE: Your

instructor may substitute another matched pair for the

3096 array. Consult your TA for more information.

6. Determine the common mode rejection ratio CMRR

at 1 kHz for the modified differential amplifier.

___________________________________________

MILESTONE #4-1: Demonstrate that your final

circuit functions well as a differential amplifier.

___________________________________________

Experiment #5

High-frequency Behavior of MOSFET's

Session #8 and #9

Introduction

The objective of this lab is to measure the components

in the small-signal model of the MOSFET and to

investigate the high frequency response of some

amplifier circuits using it. The diagram below shows a

small signal high frequency equivalent of a MOSFET.

The component ro will be ignored in the experiment

because it will be shunted by a much smaller load

resistor. The 2N7000 n-channel enhancement mode

MOSFETs in your lab kit will be used for this

experiment.


Experiment

1. Construct the common source amplifier shown.

Determine the transconductance of the transistor at

midband frequencies and the midband gain Vo/Vi.

Bias the transistor at a drain current of approximately

2 mA and a dc drain-source voltage of 8 V. CG and

CS are intended to be short circuits at midband

frequencies as low as 1 kHz so choose them

appropriately. Set Rg to 5kΩ. Notice that RG1 and

RG2 shunt the input so they will have to be chosen so

as to maintain the high input impedance that a

common source amplifier is capable of having. Set

RD = RS and use VDD = 15-16V.

__________________________________________

MILESTONE #5-1: Demonstrate your measurement

of the MOSFET transconductance.

__________________________________________

2. Measure the high frequency 3db down fH circuit

designed in step #1.

The voltage gain of the amplifier vo/vg versus

frequency shows an approximate single-pole behavior

with the frequency of the pole given by

fH = 1/{2Rg||RG1||RG2}[Cgs+ Cgd(1 + gmRD)]}

where fH is the frequency at which the voltage gain

has fallen 3 dB from its mid-band value.

You now have one equation in the 2 MOSFET

parameters, Cgs, and Cgd. You already have a value

of gm from step #1.

3. Now measure fH again, this time a resistor RD

equal to one half the value used in steps #1 and #2.

Now you have a second equation in the two unknown

quantities along the value of gm measured in step #1 .

4. Solve the 3 equations that result from the

measurements (steps 1,2 and 3) to determine the

values of Cgs, and Cgd.

Cascode Amplifier

You have observed the connection between the

midband gain and the bandwidth of the common

source amplifier with the bandwidth decreasing as the

midband gain increases. A circuit which allows

greater bandwidth at a given gain is the cascode which

is a common source / common gate pair (CS-CG)

5. Build a cascode amplifier using the figure below as

a guide. Measure the gain and bandwidth of this

circuit and compare with the values obtained earlier

in this lab

The bais points of the two transistors in the CD-CG

amplifier should be the same as the transistor in the

CS amplifier, i.e. a drain current of about 2 mA. Also

RS, RD, and Rg in the cascode circuit should be the

same as the common source amplifier. This will make

the bandwidth comparison between the two amplifiers

as consistent as possible.

___________________________________________

+

-

C gs r o

g m

V gs

V gs

+

-

v ds

S S

Amplifier

G

C gd


MILESTONE #5-2: Demonstrate that your cascode

amplifier has a reasonable dynamic range and explain

how the gain and bandwidth were measured.

___________________________________________

6. Measure the gain and bandwidth of the common

drain/common gate amplifier (CD-CG pair) shown

below for comparison with the common source and

cascode amplifiers. Design the bias points of the

MOSFET to be the same as in step #5 as closely as

convenient. Again set Rg to 5 kΩ

___________________________________________

MILESTONE #5-3: Demonstrate that your CD-CG

amplifier has a reasonable dynamic range and a

bandwidth exceeding the previous two amplifier

configurations.

__________________________________________

Quiz #2 - Exps. 1-5

Session #10

Experiment #6

Operational Amplifiers

Sessions #11 and #12

Introduction

This lab will investigate some of the non-ideal

operating behavior of the 741 opamp, with particular

emphasis on frequency response characteristics. In

addition, opamp use in the design of active filters will

be studied. The op amps are to be operated from 15

V supplies, unless otherwise stated.

Experiment

Operating Characteristics

1. Use the circuit of Fig.67-1 to determine the low

frequency (i.e. dc) open loop gain Av of the 741 op

amp in your lab kit. Use a low frequency (less than 5

Hz) sine wave or triangle wave signal for the input

Vin. Control the amplitude of the input so that the

output waveform is not distorted.

Show the derivation of the equation for the open loop

voltage given below in your lab notebook. The

derivation assumes the op amp has infinite input

resistance, zero output resistance and a finite voltage

gain Av Vout and Vin have a phase difference of 180º.

Av = -Vout

Vout +Vin3x104 = -

Vout

|Vout | - |Vin |3x104

R g C G2

R G1

R D

V DD

R S C S

v o

+

- v g

+

-

R G2

C G

Cascode

R G3


Figure 6-1. Test scircuit for measuring the dc open

loop gain of an op amp.

2. Construct an inverting amplifier with a voltage

gain 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. Use

the oscilloscope for this purpose.

3. 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 frequency

value. Use these results to deduce the open loop pole

frequency (i.e. cutoff or 3db down frequency) of the

op amp.

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

unity-gain voltage follower with a square wave input

signal vs(t) at 50 kHz.

Also investigate the effect of the slew rate on

sinusoidal input signals of various amplitudes and

frequencies. Does the relationship between the slew

rate, the signal frequency, and the maximum

undistorted output amplitude agree with theory?

___________________________________________

MILESTONE #6-1: Demonstrate the slew rate

limitation effect to your instructor or TA.

___________________________________________

Active Filters

5. Construct the circuit shown below and determine

its transfer characteristic and its cutoff frequency f3dB.

Figure 6-2. Active filter circuit.

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 #6-2: Demonstrate the transfer

characteristic of the active filter and its cutoff

frequency. PSPICE DEMO: Bring the results of a

PSPICE simulation of the amplifier (an AC sweep)

and demonstrate that the simulation reproduces what

you have just demonstrated on the lab bench.

___________________________________________

6. Construct the circuit shown below and determine

its transfer characteristic and its cutoff frequency f3dB.


Figure 6-3. Active filter circuit


Compare the cutoff frequency with the theoretical

value of:

3dB = 1/(1.414RC) .

Compare the roll off (in dB/decade) of this filter with

that of Item 4.

7. Construct the circuit shown below. Determine its

transfer characteristic and the center frequency fo at

which the gain is a maximum.


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 parameter

Q = of varying R and compare with theory.

Figure 6-4. Active filter circuit.

___________________________________________

MILESTONE #6-3: Demonstrate the transfer

characteristic of the active filter of Item 7.

Experiment #7

Feedback Amplifiers

Sessions #13 and #14

This experiment explores the characteristics of

feedback amplifiers including stability issues and how

to compensate such amplifiers. In the first four steps

of this exercise you will explore the four feedback

topologies.

Preview: You must know the following about

each of the four feedback topologies and

the equations for each should be in your

lab notebook:

a. The closed-loop voltage gain (the transfer

function)

b. The feedback factor (β)

c. The input and output resistances with feedback

d. The 3-dB frequency


Series/Shunt Feedback

1. Design the series/shunt topology shown above for a

midband no-load voltage gain of about 15 and

measure the midband voltage gain for various

resistive loads. Also determine the low-frequency

small-signal input resistance and the location of the

dominant pole in the sinusoidal steady state response.

Deduce the location of the dominant pole in the open

loop response of the op-amp itself.

___________________________________________

MILESTONE #7-1: Your TA will tell you which one

of your amplifiers from items 1 through 4 to leave

connected. When you have completed item 4

demonstrate that amplifier.

___________________________________________

Shunt/Series

2. Design for a mid-band short-circuit current gain of

about 100 and measure the mid-band value for

various resistive loads.

In this case the input current source is to be

approximated with a voltage source in series with a

large resistance (e.g. 1M).

Series/Series

3. Design for a mid-band short-circuit

transconductance of about 1 ma/v and measure the

mid-band transconductance for various resistive

loads.

Shunt/Shunt

4. Design for a mid-band open-circuit trans-

resistance of about 100 k and measure the mid-band

trans-resistance for various resistive loads.

Frequency Response

5. Connect 2 identical amplifiers as designed in item 1

in series and provide overall feedback to make the

overall voltage gain about 15 at mid-band.


(Remember that the dc offset voltage of opamp #1 is

amplified by #2 and this may cause saturation. You

may have to do something about this.)

i. Measure the frequency response of this

compound amplifier.

ii. Examine the output for input square waves of

various frequencies.

iii. Determine the Q of the circuit.

___________________________________________

MILESTONE #7-2: Demonstrate the response of this

circuit to square waves of various frequencies.

___________________________________________

Stability

6. Connect 3 identical amplifiers as designed in item 1

in series (cascade) and provide overall feedback so as

to give an overall mid-band voltage gain variable

from 10 to 100. In other words, insert a series-shunt

stage between the two amplifier stages in step #5.

Investigate the stability of the circuit as a function of

gain.

Compensation

7. For the 3-stage amplifier of item 6 determine a

dominant pole compensation to give stability with a

phase margin between 45 and 90 degrees.

Find a way to add this pole to your circuit and

determine experimentally the bandwidth of the

compensated amplifier. (Suggestion: inserting the

following network between stages is one way to do it.)

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MILESTONE #7-3: demonstrate that the phase

margin is in the range specified.

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Documents

EE3101 Lab Manual 2013 UMN