ECE 2201 Electrical & Computer Engineering Lab I

Electronic Circuits Lab Manual

Semester I 2008/2009

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LAB V SAFETY Safety in the electrical laboratory, as everywhere else, is a matter of the knowledge of potential hazards, following safety precautions, and common sense. Observing safety precautions is important due to pronounced hazards in any electrical/computer engineering laboratory. Death is usually certain when 0.1 ampere or more flows through the head or upper thorax and have been fatal to persons with coronary conditions. The current depends on body resistance, the resistance between body and ground, and the voltage source. If the skin is wet, the heart is weak, the body contact with ground is large and direct, then 40 volts could be fatal. Therefore, never take a chance on "low" voltage. When working in a laboratory, injuries such as burns, broken bones, sprains, or damage to eyes are possible and precautions must be taken to avoid these as well as the much less common fatal electrical shock. Make sure that you have handy emergency phone numbers to call for assistance if necessary. If any safety questions arise, consult the lab demonstrator or technical assistant/technician for guidance and instructions. Observing proper safety precautions is important when working in the laboratory to prevent harm to yourself or others. The most common hazard is the electric shock which can be fatal if one is not careful. Acquaint yourself with the location of the following safety items within the lab.

a. fire extinguisher b. first aid kit c. telephone and emergency numbers

ECE Department 03-2056 4530

Kulliyyah of Engineering Deputy Dean’s Student Affairs 03-2056 4447

IIUM Security 03-2056 4172

IIUM Clinic 03-2056 4444

Electric shock Shock is caused by passing an electric current through the human body. The severity depends mainly on the amount of current and is less function of the applied voltage. The threshold of electric shock is about 1 mA which usually gives an unpleasant tingling. For currents above 10 mA, severe muscle pain occurs and the victim can't let go of the conductor due to muscle spasm. Current between 100 mA and 200 mA (50 Hz AC) causes ventricular fibrillation of the heart and is most likely to be lethal.

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What is the voltage required for a fatal current to flow? This depends on the skin resistance. Wet skin can have a resistance as low as 150 Ohm and dry skin may have a resistance of 15 kOhm. Arms and legs have a resistance of about 100 Ohm and the trunk 200 Ohm. This implies that 240 V can cause about 500 mA to flow in the body if the skin is wet and thus be fatal. In addition skin resistance falls quickly at the point of contact, so it is important to break the contact as quickly as possible to prevent the current from rising to lethal levels. Equipment grounding Grounding is very important. Improper grounding can be the source of errors, noise and a lot of trouble. Here we will focus on equipment grounding as a protection against electrical shocks. Electric instruments and appliances have equipments casings that are electrically insulated from the wires that carry the power. The isolation is provided by the insulation of the wires as shown in the figure a below. However, if the wire insulation gets damaged and makes contact to the casing, the casing will be at the high voltage supplied by the wires. If the user touches the instrument he or she will feel the high voltage. If, while standing on a wet floor, a user simultaneously comes in contact with the instrument case and a pipe or faucet connected to ground, a sizable current can flow through him or her, as shown in Figure b. However, if the case is connected to the ground by use of a third (ground) wire, the current will flow from the hot wire directly to the ground and bypass the user as illustrated in figure c.

Equipments with a three wire cord is thus much safer to use. The ground wire (3rd wire) which is connected to metal case, is also connected to the earth ground (usually a pipe or bar in the ground) through the wall plug outlet.

Always observe the following safety precautions when working in the laboratory:

1. Do not work alone while working with high voltages or on energized electrical equipment or

electrically operated machinery like a drill.

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2. Power must be switched off whenever an experiment or project is being assembled, disassembled, or modified. Discharge any high voltage points to grounds with a well insulated jumper. Remember that capacitors can store dangerous quantities of energy.

3. Make measurements on live circuits or discharge capacitors with well insulated probes keeping

one hand behind your back or in your pocket. Do not allow any part of your body to contact any part of the circuit or equipment connected to the circuit.

4. After switching power off, discharge any capacitors that were in the circuit. Do not trust supposedly discharged capacitors. Certain types of capacitors can build up a residual charge after being discharged. Use a shorting bar across the capacitor, and keep it connected until ready for use. If you use electrolytic capacitors, do not :

• put excessive voltage across them • put ac across them • connect them in reverse polarity

5. Take extreme care when using tools that can cause short circuits if accidental contact is made to other circuit elements. Only tools with insulated handles should be used.

6. If a person comes in contact with a high voltage, immediately shut off power. Do not attempt to remove a person in contact with a high voltage unless you are insulated from them. If the victim is not breathing, apply CPR immediately continuing until he/she is revived, and have someone dial emergency numbers for assistance.

7. Check wire current carrying capacity if you will be using high currents. Also make sure your leads are rated to withstand the voltages you are using. This includes instrument leads.

8. Avoid simultaneous touching of any metal chassis used as an enclosure for your circuits and any pipes in the laboratory that may make contact with the earth, such as a water pipe. Use a floating voltmeter to measure the voltage from ground to the chassis to see if a hazardous potential difference exists.

9. Make sure that the lab instruments are at ground potential by using the ground terminal supplied on the instrument. Never handle wet, damp, or ungrounded electrical equipment.

10. Never touch electrical equipment while standing on a damp or metal floor. 11. Wearing a ring or watch can be hazardous in an electrical lab since such items make good

electrodes for the human body. 12. When using rotating machinery, place neckties or necklaces inside your shirt or, better yet,

remove them. 13. Never open field circuits of D-C motors because the resulting dangerously high speeds may cause

a "mechanical explosion". 14. Keep your eyes away from arcing points. High intensity arcs may seriously impair your vision or

a shower of molten copper may cause permanent eye injury. 15. Never operate the black circuit breakers on the main and branch circuit panels.

16. In an emergency all power in the laboratory can be switched off by depressing the large red button on the main breaker panel. Locate it. It is to be used for emergencies only.

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17. Chairs and stools should be kept under benches when not in use. Sit upright on chairs or stools keeping the feet on the floor. Be alert for wet floors near the stools.

18. Horseplay, running, or practical jokes must not occur in the laboratory.

19. Never use water on an electrical fire. If possible switch power off, then use CO2 or a dry type fire extinguisher. Locate extinguishers and read operating instructions before an emergency occurs.

20. Never plunge for a falling part of a live circuit such as leads or measuring equipment. 21. Never touch even one wire of a circuit; it may be hot. 22. Avoid heat dissipating surfaces of high wattage resistors and loads because they can cause severe

burns. 23. Keep clear of rotating machinery.

Precautionary Steps Before Starting an Experiment so as Not to Waste Time Allocated

a) Read materials related to experiment before hand as preparation for pre-lab quiz and experimental calculation.

b) Make sure that apparatus to be used are in good condition. Seek help from technicians

or the lab demonstrator in charge should any problem arises. • Power supply is working properly ie Imax (maximum current) LED indicator is

disable. Maximum current will retard the dial movement and eventually damage the equipment. Two factors that will light up the LED indicator are short circuit and insufficient supply of current by the equipment itself. To monitor and maintain a constant power supply, the equipment must be connected to circuit during voltage measurement. DMM are not to be used simultaneously with oscilloscope to avert wrong results.

• Digital multimeter (DMM) with low battery indicated is not to be used. By proper connection, check fuses functionality (especially important for current measurement). Comprehend the use of DMM for various functions. Verify measurements obtained with theoretical values calculated as it is quite often where 2 decimal point reading and 3 decimal point reading are very much deviated.

• The functionality of voltage waveform generators are to be understood. Make sure that frequency desired is displayed by selecting appropriate multiplier knob. Improper settings (ie selected knob is not set at minimum (in direction of CAL – calibrate) at the bottom of knob) might result in misleading values and hence incorrect results. Avoid connecting oscilloscope together with DMM as this will lead to erroneous result.

• Make sure both analog and digital oscilloscopes are properly calibrated by positioning sweep variables for VOLT / DIV in direction of CAL. Calibration can also be achieved by stand alone operation where coaxial cable connects CH1 to bottom left hand terminal of oscilloscope. This procedure also verifies coaxial cable continuity.

c) Internal circuitry configuration of breadboard or Vero board should be at students’

fingertips (ie holes are connected horizontally not vertically for the main part with engravings disconnecting in-line holes).

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d) Students should be rest assured that measured values (theoretical values) of discrete components retrieved ie resistor, capacitor and inductor are in accordance the required ones.

e) Continuity check of connecter or wire using DMM should be performed prior to

proceeding an experiment. Minimize wires usage to avert mistakes.

f) It is unethical and unislamic for students to falsify results as to make them appear exactly consistent with theoretical calculations.

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LAB VI

EXPERIMENT 1

SMALL SIGNAL CE AMPLIFIERS

1. OBJECTIVE • To demonstrate the ac operation of the common-emitter (CE) amplifier. • To demonstrate the effects that a bypass capacitor has on amplifier voltage gain (Av).

2. DISSCUSSION The input signal to a CE amplifier is applied across the base-emitter junction of the device. The output from this circuit is taken from the collector terminal of the transistor. The CE amplifier is one of the most commonly used BIT amplifier configurations. The amplifier has a relatively high voltage gain, a relatively high current gain, and a voltage phase shift of 1800 between its input (base) and output (collector) terminals. In this exercise, you will observe the ac operation of the CE amplifier. You will also observe the effects of the emitter bypass capacitor, a component used to increase the voltage gain of the CE amplifier.

Figure 1

3. MATERIALS

1 Variable dc power supply 1 Variable ac signal generator 1 Dual-trace oscilloscope 1 DMM 1 2N3904 npn transistor 5 Resistors: 390 Ω, 1.5 kΩ, 2.2 kΩ, 3.3 kΩ, and 100 kΩ 1 50-kΩ Potentiometer 2 10-μF Electrolytic capacitors 1 100- μF Electrolytic capacitor

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4. USEFUL FORMULAS

VA =in

out

VV

VA =e

C

rr′

5. PROCEDURE A. Construct the circuit shown in fig. 1. B. Apply power to the circuit and adjust R1a to provide midpoint bias. C. For future reference, measure and record the value of VC and VE.

Vc = VE =

D. Apply a 1-kHz, 20-m Vpp ac signal to the input of the amplifier.

Note: You should set the signal generator so that you have 20 m VPP at the base terminal of the transistor (measured with respect to ground).

E. Measure and record the peak-to-peak output voltage at the collector terminal of the transistor.

Vout = Vpp.

F. Using the values measured in steps 4 and 5, calculate the voltage gain of the amplifier. Av=

G. The coupling capacitors in an amplifier are used to block dc while coupling an ac signal. In other words, when you have an ac signal with some measurable dc average on one side of the capacitor, you should get only the ac signal on the other side. The dc average of the signal should be eliminated. Using your dc voltmeter, measure the dc average of the ac signal on the transistor side of CC2. Vave = on the transistor side of CC2.

H. Measure and record the dc average of the ac signal on the load side of CC2. Vave = on the load side of CC2

I. Do your measurements support the statement that a coupling capacitor passes ac while blocking dc?

J. It was stated in the Discussion section of this exercise that the CE amplifier produces a 1800

voltage phase shift from input (base) to output (collector). Connect channel 1 of your oscilloscope to the base of the transistor and channel 2 to the collector. Adjust the vertical sensitivity of your channels so that each signal fills approximately four major divisions on the CRT. Neatly draw the display on your oscilloscope on the grid provided.

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K. Remove the emitter bypass capacitor and repeat steps 4, 5, and 6 of the procedure. Vin = Vpp Vout = Vpp Av =

L. What happened to Av when the bypass capacitor was removed? Why?

QUESTIONS AND PROBLEMS 1) The voltage gain of a CE amplifier, employing an emitter bypass capacitor, can be found as

VA =e

C

rr

′ Where Cr = CR || LR

Another form of this equation allows us to calculate the ac resistance of the emitter (r'e) as follows:

er ′ =V

C

Ar

Using the measured value of Av (from step 6 of the procedure) and the value of rc, calculate the value of r'e.

r'e=

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2) The value of r'e can be approximated as

r'e =EImV25

Where

E

EE R

VI =

Using your circuit values and this equation, calculate the value of r'e . r´e =

3) What is the percent of error between the two values of r’e that you have calculated? % of error = How would you account for this percent of error?

4) Which value of r’e do you believe to be more accurate? Explain your answer. 5) When the emitter resistor is not bypassed, the voltage gain of a CE amplifier can be approximated

as

E

CV R

rA =

Using the rated values of RC, RL, and RE, calculate the value of Av for the unbypassed circuit. Av=

6) Calculate the percent of error between the calculated value of Av (question 5) and the measured value (procedure step 11). % Of error = How would you account for this percent of error?

7) With respect to circuit bias, why is it important to block the dc reference of the signal, as you observed in steps 7 and 8?

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LAB VII

EXPERIMENT 2

SMALL SIGNAL CS AMPLIFIERS

1. OBJECTIVES

• To demonstrate the ac operation of a typical common-source amplifier. • To demonstrate the differences between the ac operating characteristics of a typical JFET

amplifier and those of a typical BJT amplifier 2. DISCUSSION There are several similarities between the common-source (CS) amplifier and the common-emitter (CE) amplifier. Both amplifiers provide a measurable amount of voltage gain. Both amplifiers have a 1800 voltage phase shift between the input and output terminals. At the same time, there are several differences between the two amplifier types. Perhaps the biggest difference is that JFETs are voltage-controlled devices while BJTs are current-controlled devices. The CS amplifier typically has much higher input impedance than the CE amplifier. Also, the voltage gain calculation for a CS amplifier is different from the CE voltage gain calculation. In this exercise, you will observe the operation of a self-biased CS amplifier. While analyzing this exercise, you should pay close attention to those points of operation that distinguish the CS amplifier from the CE amplifier.

Figure.1

3. MATERIALS

1 Variable dc power supply 1 Variable ac signal generator 1 Dual-trace oscilloscope 1 VOM or dc milliammeter 1 DMM 1 2N5485 n-channel JFET 2 Resistors: 4.7 kΩ and 1 MΩ 2 Potentiometers: 5 kΩ and 2.0 MΩ 2 Capacitors: 0.022 μF and 22 μF

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4. USEFUL FORMULAS Av =gmrD

in

outV v

vA =

5. PROCEDURE

A. Construct the circuit in Fig.1. RS should be set initially to 1 kΩ. B. The value of gm for a JFET is found as

GS

Dm V

Ig ∆=

In this step, you will determine the value of gm for your JFET as follows: • With RS set to 1 kΩ, measure and record the following:

VGS =

ID = • Power down and adjust Rs to a value of 1.5 kΩ. Power up the circuit and measure and

record the following:

VGS =

ID = • Calculate the following:

ΔVGS = VGS(max) - VGS(min) =

ΔID = ID(max) -ID(min) =

gm =

GS

D

VI

∆∆ =

C. Using the rated value of RD, calculate the open-load voltage gain of your amplifier. Av= D. Set RS to approximately 1.3 kΩ. E. Set the amplitude of your signal generator to minimum. Set the output frequency of your

signal generator to approximately 1 kHz. F. Connect your oscilloscope to the output of the amplifier. Then increase the amplitude of the

input signal until you get the maximum undistorted output from the amplifier. Measure and record the following:

Vout = Vpp Vjn = Vpp G. Using the values obtained in step F, calculate the value of Av for your amplifier. Av=

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H. Adjust the vertical sensitivity of your oscilloscope channels so that you can observe both the input and output waveforms on the CRT at the same time. Then neatly draw the two waveforms in their proper phase relationships on the grid provided.

Note: For steps I through K, use the ×l0 position on the scope probes. I. Without disturbing the amplitude setting or your signal generator, insert the 2 MΩ

potentiometer between the generator output and the input coupling capacitor. J. Adjust the 2 MΩ potentiometer until the output from the amplifier has an amplitude that is

one-half of its original value. K. Without disturbing the potentiometer setting, remove it from the circuit and measure its

resistance. This is approximately equal to the input impedance of the amplifier. R ≈ Zjn=

QUESTIONS AND PROBLEMS

1) Calculate the percent of error between the values of Av obtained in steps 3 and 7 of the procedure.

% of error =

How would you account for this error?

2) Calculate the percent of error between the measured input impedance of the amplifier and the

rated value of RG. % Of error =

Why wasn't the input impedance of the JFET considered in the percent of error calculation?

3) Discuss, in your own words, what you observed in this exercise.

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LAB VIII

EXPERIMENT 3

INVERTING AMPLIFIERS

1. OBJECTIVES

• To demonstrate the operation of the inverting amplifier. • To demonstrate the effect of resistor faults on the operation of the inverting amplifier.

2. DISCUSSION The inverting amplifier is very similar in several respects to the common-emitter (CE) and common-source (CS) amplifiers. Like the CE and CS circuits, the inverting amplifier produces a 1800 voltage phase shift between its input and output terminals. Inverting amplifiers can also be designed for a wide range of voltage gains. At the same time, the inverting amplifier has many characteristics that make it more desirable than either the CE or CS amplifiers:

i. Inverting amplifiers are capable of extremely high voltage gains, up to 100,000 and higher in many cases.

ii. The gain of an inverting amplifier is extremely stable and easy to calculate. iii. Inverting amplifiers are easier and often cheaper to design and troubleshoot than either CE or

CS amplifiers. Since this is probably your first exposure to working with integrated-circuit (IC) op-amps, there are a few points that should be made:

i. The +V and -V pins must be connected to their respective supply voltages for the op-amp to work.

ii. Pin 1 is identified by an indentation in the IC package, as shown below. When the indentation is on the left, pin 1 is at the lower-left corner of the IC. The rest of the pins are numbered in sequence, going counterclockwise from pin 1.

iii. The op-amp will not work if either the inverting (pin 2) or the noninverting (pin 3) inputs are left open.

iv. You should never apply an input signal to an op-amp unless both supply voltages are present.

Figure 1

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Figure 2 3. MATERIALS

1 DMM 1 Dual-polarity variable dc power supply 1 Variable ac signal generator 1 Dual-trace oscilloscope 1 μA741 Op-amp (or equivalent) 9 Resistors: 470 Ω, 1 kΩ, 10 kΩ (3), 27 kΩ, 39 kΩ, 47 kΩ, and 82 kΩ 1 1-kΩ Potentiometer

4. USEFUL FORMULAS

i

fCL R

RA = (calculated)

in

outCL V

VA = (measured)

(Note: ACL is used in place of Av whenever output-to-input feedback is used. The subscript CL is used to denote closed-loop voltage gain.)

5. PROCEDURE

Part I. Operation

A. Construct the circuit shown in fig. 2. B. Apply power to the circuit. Adjust the signal generator for a 1-V PP output at a frequency of

500 Hz. Apply the input signal to the amplifier. Note: If you are using a function generator with dc offset controls, make sure that the offset is set at 0 V.

C. Set up your oscilloscope to measure the circuit input and output wave forms simultaneously. Draw these waveforms on the grid provided.

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D. Calculate the value of ACL for the circuit.

ACL= E. Measure and record the peak-to-peak input and output voltages.

Vin = Vpp Vout = Vpp

F. Using the values of Vin and Vout from step 5, calculate the value of ACL for the circuit. ACL=

G. Calculate the percent of error between the values obtained in steps 4 and 6 of the procedure. % of error =

H. Below Table 1 contains a series of resistance values to be used in place of Rf in the circuit. For each value of Rf, repeat steps 4 through 7. Record your measured and calculated values in the appropriate spaces in the table. TABLE 1

Table 1

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I. Increase the input level to 5 Vpp. Return Rf to 10 kΩ. Connect a l0-kΩ resistor as a load. Measure the voltage gain of the amplifier. Change RL to 1-kΩ and then to 470Ω. For each value, measure the voltage gain. ACL = (RL = 10 kΩ) ACL = (RL=1 kΩ) ACL = (RL = 470 Ω) How did the changing load affect the amplifier voltage gain?

J. Now set the l-kΩ potentiometer to its maximum setting and connect it as the load. Slowly decrease the value of RL until the amplifier voltage gain starts to decrease and the waveform starts to distort or clip. Remove the potentiometer and measure and record this value. RL=

Part II. Fault Symptoms

K. Remove Rf from the circuit. Observe the circuit output waveform and draw it on the grid provided. Note: Whenever you are directed to remove a component, a gap should be left where the com-ponent appeared in the circuit. Do not bridge the gap left by the missing component unless directed to do so.

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L. Return Rf to the circuit and remove Ri. Draw the resulting output on the grid provided.

QUESTIONS AND PROBLEMS

1) How would you account for the percents of error obtained in steps 7 and 8 of the procedure? 2) Based upon your knowledge of op-amps, explain why the voltage gain responded as it did to the

changes in load recorded in step 9. 3) Based upon your knowledge of the output impedance of op-amps, explain why the waveform

started to clip at the load value recorded in step 10. 4) How would you account for the output waveform observed in step 11 of the procedure?

5) How would you account for the output waveform observed in step 12 of the procedure?

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LAB IX

EXPERIMENT 4

NONINVERTING AMPLIFIERS

1. OBJECTIVE

• To demonstrate the operation of the non-inverting amplifier. • To demonstrate the effects of resistor faults on the operation of the non-inverting amplifier.

1. DISCUSSION The non-inverting amplifier has many of the characteristics of the inverting amplifier. There are two exceptions. As the name implies, the output of this amplifier is in phase with its input; that is, there is no 1800 voltage phase shift. Also, the non-inverting amplifier has significantly higher input impedance than a comparable inverting amplifier. If you look at Fig. 1 below, you can see that the input is connected directly to the non-inverting terminal of the op-amp. As a result, the circuit input impedance is equal to (or greater than) the input impedance of the op-amp itself. When compared to discrete amplifier circuits like the emitter or source follower, the non-inverting amplifier shares some of their characteristics. It has high input impedance and low output impedance, and the input and output signals are in phase. The one major difference is that the non-inverting amplifier can have high voltage gain, whereas the emitter and source followers are limited to voltage gains slightly less than unity. In this exercise, you will investigate the basic operation of the non-inverting amplifier.

Figure 1

2. MATERIALS

1 DMM 1 Dual-polarity variable dc power supply 1 Variable ac signal generator 1 Dual-trace oscilloscope 1 μA7 41 Op-amp (or equivalent) 6 Resistors: 10 kΩ (2), 27 kΩ, 39 kΩ, 47 kΩ, and 82 kΩ

4. USEFUL FORMULAS

1+=i

fCL R

RA (calculated)

20

in

outCL V

VA = (measured)

5. PROCEDURE

Part I. Circuit Operation

A. Construct the circuit shown in Figure shown above. B. Adjust your signal generator output for a 1-Vpp output at a frequency of 500 Hz. Apply the

signal to the amplifier input. (Note: If you are using a function generator with dc offset controls, make sure that the offset is set at 0 V.)

C. Set your oscilloscope so that you can observe the circuit input and output signals simultaneously. Draw the waveforms on the grid provided.

D. Measure and record the peak-to-peak input and output voltages of the amplifier. Vin = Vpp Vout = Vpp

E. Using the values of Vin and Vout measured in step 4, calculate the voltage gain of the amplifier. ACL=

F. Calculate the voltage gain of the amplifier using the values of Rf and Ri. ACL=

G. Calculate the percent of error between the values of ACL found in steps 5 and 6. % Of error =

H. For each of the values of Rf shown in Table 1, repeat steps 4 through 7.

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Table 1

Part II. Fault Symptoms I. Remove the feedback resistor (Rf) from the circuit. Observe the resulting circuit output waveform

and draw it on the grid provided.

Note: Whenever you are directed to remove a component, a gap should be left where the com-ponent appeared in the circuit. Do not bridge the gap left by the missing component unless directed to do so.

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J. Return the feedback resistor to the circuit and remove the input resistor (Ri ). Draw the resulting

circuit output on the grid provided.

QUESTIONS AND PROBLEMS

1) How would you account for the percent of error values obtained in steps 7 and 8 of the procedure? 2) How would you explain the output observed in step 9 of the procedure?

3) How would you explain the output observed in step 10 of the procedure?

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LAB X

EXPERIMENT 5

SUMMING AMPLIFIERS

1. OBJECTIVE • To demonstrate the operation of a basic summing amplifier. 2. DISCUSSION The summing amplifier is an op-amp circuit that accepts several inputs and then produces an output that is proportional to the sum of these inputs. The term proportional is used because the circuit mayor may not have gain, and the circuit output is inverted. The inputs can be dc or ac values. In this exercise, you will investigate a two-input summing amplifier using sine wave inputs. It should be noted that op-amp 1 in Figure shown below, is used simply as a buffer.

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Figure 1 3. MATERIALS 1 DMM 1 Dual-polarity variable dc power supply 1 Variable ac signal generator 1 Oscilloscope 2 μA.741 Op-amps or equivalents 5 Resistors: 10 kΩ (3), 22 kΩ, and 33 kΩ. 4. USEFUL FORMULA

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5. PROCEDURE A. Construct the circuit shown above. Note: In Figure above, the signal generator is supplying the two input signals to the

summing amplifier (op-amp 2). Op-amp 1 is used to provide isolation between the summing amplifier inputs

B. Apply power to the circuit. Adjust the signal generator for a 1-Vpk, 300-Hz output. Using the equation given above, predict the output from the summing amplifier when V1 = V2 = 1 Vpk.

Vout =------------------- C. Using the equation given above, predict the output from the summing amplifier when V1

= V2 = 1 Vpk. Vout =-------------------

D. Measure and record the peak output voltage. Vout =------------------- E. Replace R1 with the 22-kΩ resistor. Using this value in the original equation, predict the

output from the summing amplifier when V1 = V2 = 1 Vpk Vout =--------------------- F. Measure and record the peak output voltage. Vout =-------------------- G. Replace Rf with the 33-kΩ resistor and return R1 to its original value. Predict the output

voltage for the circuit with V1 = V2 = 1 Vpk Vout =--------------------- H. Measure and record the peak output voltage. Vout =--------------------- I. Replace Rf with the 22-kΩ resistor. Predict the output voltage for the circuit with V1 = V2 = 1 Vpk Vout =--------------------- J. Measure and record the peak output voltage. Vout =-------------------- K. Predict the output voltage for each V1, V2 combination shown Table below.

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L. Set the signal generator so that its peak output voltage is equal to each V1, V2 combination

shown above (Table). For each input combination, measure and record the peak output voltage.

QUESTIONS AND PROBLEMS 2. Calculate the percent of error between your predicted and measured values of Vout in steps

3 and 4 of the procedure. % of error =----------------------------------- How would you account for this error? 2) Compare your measurements in steps 4 and 6 of the procedure. Based on the two values,

what effect does increasing the value of an input resistor have on the output from a summing amplifier?

3) Compare your measurements in steps 4 and 8 of the procedure. Based on the two values,

what effect does increasing the value of the feedback resistor have on the output from a summing amplifier?

4) Discuss, in your own words, what you observed in this exercise.