Elecs1 Lab-manual 2003

7/27/2019 Elecs1 Lab-manual 2003

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CONTENTS

TITLE PAGE PAGE OVERVIEW 2

GENERAL SAFETY RULES IN THE LABORATORIES AND SHOPS 3

ELECTRICAL HAZARD CATEGORY 4

EXPERIMENT NO. 1 CATHODE RAY OSCILLOSCOPE 6

EXPERIMENT NO. 2 DIODE CHARACTERISTICS 11

EXPERIMENT NO. 3 ZENER DIODE CHARACTERISTICS 15

EXPERIMENT NO. 4 ZENER REGULATION 18EXPERIMENT NO. 5 WAVE RECTIFIER 21

EXPERIMENT NO. 6 CLIPPER CIRCUITS 27

EXPERIMENT NO. 7 BJT CIRCUIT FIXED-BIAS 33

EXPERIMENT NO. 8 JFET CHARACTERISTICS 38

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OVERVIEW

In the advent of electronics technology one of the most remarkable electronic component inventedby man is diode which is in the category of semiconductor the discovery of semiconductor also yield foranother discoveries like transistor. That is why, it is important for an aspiring engineer to have a solidbackground about the two components.

The manual is intended for third year level engineering students who wish to study electronicscircuits this will also serve as a preparatory for electronics analysis and circuit design. It is compose of 8experiments that will enhanced students ability to analyze the circuit and to properly used the electronicsequipment with confidence.

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ELECTRICAL HAZARD CATEGORY

1. Electrical shock2. Hazard in the electrical burns

3. Effects of blast which include pressure impact flying particles from vaporized conductors and first breatheconsideration.

Electrical ShockElectric shock occurs when the body becomes part of an electrical circuit. Shocks can happen in threeways.

A person may come in contact with both conductors in a circuit. A person may provide a path between an ungrounded conductor and the ground. A person may provide a path between the ground and a conducting material that is in contact withan ungrounded conductor.The terms high voltage and low voltage are relative terms. In transmission-line terminology, "lowvoltage" is much higher than the 600 volts. At home, you would not think of 600 volts as being lowvoltage.Even when applied to 120-volt circuits, the term low voltage is deceiving. To some people low voltagemeans low hazard. Actually, low voltage does not necessarily mean low hazard, because potentialdifference is only one factor making up the dangerous effects of electricity.

THE EXTENT OF INJURY ACCOMPANYING ELECTRIC SHOCK DEPENDS ON THREE FACTORS

The amount of current through the body.

The length of time a person is subjected to the current.

The path of current through the body.

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The amount of the current depends on the potential difference and the resistance. The effects of lowcurrent on the human body range from a temporary mild tingling sensation to death. An electric shockcan injure you in either or both of the following. A severe shock can stop the heart or the breathing muscles, or both. The heating effects of the current can cause severe burns, especially at points where the electricity

enters and leaves the body.Other effects include severe bleeding, breathing difficulty, and ventricular fibrillation. In addition, youmay strike something, or have some other accident as a result of your response to the shock.

THE EFFECT OF ELECTRIC CURRENT:

CURRENT IN MILLIAMPERES EFFECT

1 or less No sensation, probably not notice

1-3

Mild sensation not painful

3-10

Painful shock

10-30

Muscular control could be lost or muscleclamping

30-75

Respiratory paralysis

75-4 amperes

Ventricular fibrillation tissue begins to burn

Over 4 amperes

Heart muscle clamp and heart stop breathing

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REFERENCE:http://www.lanl.gov/safety/electrical/docs/elec_hazard_awareness_study_guide.pdf

EXPERIMENT NO. 1

CATHODE RAY OSCILLOSCOPE

I.OBJECTIVE:

To observe sine wave, square wave, triangular wave and ramp waveforms on the C.R.O.and to measure amplitude of the waveform.

II.BACKGROUND AND INFORMATION:

C.R.O. (Cathode Ray Oscilloscope) is the instrument which is used to observe signal waveforms.Signals are displayed in time domain i.e. variation in amplitude signal with respect to time is plotted on theCRO screen. X-axis represents time and Y-axis represents amplitude. It is used to measure amplitude,frequency, and phase of the waveforms. It is also used to observe shape of the waveform C.R.O. is usefulfor troubleshooting purpose. It helps us to find out gain of amplifier, test oscillator circuits. We can measureamplitude and frequency of the waveforms at the different test point in our circuit. Thus it helps us for fault

finding procedure. In dual channel C.R.O. X-Y mode is available which is used to create. Lissajouspatterns.

Latest digital storage oscilloscope display voltage and frequency directly on the LCD and does notrequire any calculations. In this practical we will measure amplitude and frequency of the differentwaveforms like sine wave, square wave, triangular wave and ramp wave.

III.MATERIALS REQUIRED:

Instruments: Function generator, oscilloscope

IV.EXPERIMENTAL PROCEDURE:

1. Connect the function generator output at the input of C.R.O. at channel 1 or at channel 2.

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http://www.lanl.gov/safety/electrical/docs/elec_hazard_awareness_study_guide.pdfhttp://www.lanl.gov/safety/electrical/docs/elec_hazard_awareness_study_guide.pdfhttp://www.lanl.gov/safety/electrical/docs/elec_hazard_awareness_study_guide.pdfhttp://www.lanl.gov/safety/electrical/docs/elec_hazard_awareness_study_guide.pdf


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2. Select proper channel i.e. if signal is connected to channel 1 select CH1 and if signal is connected tochannel 2 select CH2.

3. Adjust Time/Div knob to get sufficient time period displacement of the wave on the C.R.O. screen.

4. With fine tuning of Time/Div make the waveform steady on screen.

5. Use triggering controls if waveform is not stable.

6. Keep Volt/Div knob such that waveforms is visible on the screen without clipping.

7. Measure P-P reading along Y-axis. This reading multiplied with volt/div gives peak to peak amplitude ofthe ac i/p wave.

8. Measure horizontal division of one complete cycle. This division multiplied by time/div gives period of thei/p wave.

9. Calculate frequency using formula f=1/T.

10. Note down readings in the table.

11. Draw waveforms of sine wave, ramp and triangular in the give space.

V.TABLE/DATA:

FUNCTIONVERTICALDIVISION

(a)

VOLTS/DIV(b)

AMPLITUDE(P-P)V=a*b

HORIZONTALDIVISION

(C)

TIME/DIV(d)

TIMET=c*d

FREQ.F=1/T

SINEWAVE

SQUAREWAVE

TRIANGU-LARWAVE

RAMPWAVE

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Draw observed waveforms:

Sine wave: (Amplitude : ________ Frequency : ________)

Square wave: (Amplitude: ________ Frequency: ________)

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Triangular wave: (Amplitude: ________ Frequency: ________)

Ramp wave: (Amplitude: ________ Frequency: ________)

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VI.COMPUTATION:

VII. CONCLUSION:

VIII.QUESTIONS:

1. What is the use of C.R.O.?

2. What you will do to measure voltage which is greater than voltage limit of the C.R.O.?

3. What do you mean by dual Channel C.R.O.?

4. How to test whether C.R.O. probe is in working condition or not?

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EXPERIMENT NO. 2

DIODE CHARACTERISTICS

I.OBJECTIVE:

To study the characteristic of sil icon and germanium diode


Silicon and Germanium is a type of semiconductor with exactly four valence electrons.Semiconductor had electrical characteristics in between conductors and insulators. Diode has thecharacteristics to function as a conducting or insulating element.

III. MATERIALS REQUIRED:

Instrument: DC power supply, digital multimeter

Components: silicon (D1N4001), germanium (D1N4148)

Resistors: 1K, 1M

Tools: Breadboard

IV. EXPERIMENTAL PROCEDURE:

Part A: Forward-bias diode characteristics

1. Construct the circuit of figure 1-a with the supply (E) is set at ) 0v. Record themeasured value of the resistor.

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Figure 1-a

2. Increase the supply voltage until VD read 0.1v. Then measure the current ID and recordthe result in table 1-1

3. Repeat step 2 for the remaining settings of VD. Shown in the table 1.1

4. Replace the silicon diode by a germanium diode and complete table 1.2

5. Plot the graph on the space provided the ID versus VD for the silicon and germaniumdiodes. Complete the curve by extending the lower region of each curve to theintersection of the axis at ID=0mA and VD=0V.

Part B. Reverse-bias diode characteristics

1. Construct the circuit of figure 1-b with E is set at 20v record the measured value of theresistor.

Figure 1-b

2. Measure the voltage VD. Measure the reverse saturation current, IS

3. Repeat the above step for germanium diode

V.TABLE/DATA:

Part A (forward bias)

1. R (measured) = ________

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2. ID (measured) Fill in the table 1.1 and table 1.2

VD(V) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.75

ID(mA)

Table 1.1 (silicon diode)

VD(V) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.75

ID(mA)

Table 1.2 (Germanium diode)

Part B (reverse bias)

1. R(measured )= ________

2. Silicon Diode = ________

VD (measured) = ________

IS (measured) = ________

3. Germanium Diode = ________

VD (measured) = ________

IS (measured) = ________

Plot the/graph

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VI. COMPUTATION:

VII.CONCLUSION:

VIII.QUESTIONS:

1. How does the two curves differ? What are their similarities?

2. How do the result of step 2 compare to step 3? What are the similarities?

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EXPERIMENT NO. 3

ZENER DIODE CHARACTERISTICS

I.OBJECTIVE:

To study the characteristics of zener diode.

II.BAKCGROUND AND INFORMATION:

A zener diode is a special kind of diode which allows current to flow in the forward direction in thesame manner as an ideal diode, but will also permit it to flow in the reverse direction when the voltage isabove a certain value known as the breakdown voltage , "zener knee voltage" or "zener voltage." Thedevice was named after Clarence Zener, who discovered this electrical property. Many diodes described as"zener" diodes rely instead on avalanche breakdown as the mechanism. Both types are used. Commonapplications include providing a reference voltage for voltage regulators, or to protect other semiconductordevices from momentary voltage pulses.


Instruments: DC power supply, Digital multimeter (DMM)

Components: Diode Zener (IN1428) or equivalent

Resistors: 0.1K, 1K (2pcs.)


ZENER DIODE CHARACTERISTICS

1. Construct the circuit of figure 3. Set the DC supply to 0V and record the measuredvalue of R.

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Figure 3.

2.Set the DC supply (E) to the values appearing in table 3 and measure both VZ and VR.

Calculate zener current. IZ using ohms law given in the table and complete the table.

3. Plot IZ versus VZ using the data in table 3.

V.TABLE/DATA:

1. R(measured)= ________

2. Table 3.

E (V) 0 1 3 5 7 9 11 13 15

VZ(V)

VR(V)

IZ=VR/R(MEASURED)

VI.COMPUTATION:

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VII.CONCLUSION:

VIII.QUESTIONS:

1. Based on the experiment you perform can you explain how will you determine the zener voltage of

an specified zener diode?

2. Give some example of application of zener diode.

3. What is the proper operating condition of zener diode?

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EXPERIMENT NO. 4

ZENER REGULATION

I.OBJECTIVE:

To study the voltage regulation in zener diode regulation circuit.


The major application of zener diode is voltage regulation in dc power supplies, zener diodemaintains a constant dc voltage under proper operating conditions, technically speaking zener must beoperated in reverse-breakdown region.


Instruments

DC power supply, function generator, digital multimeter (DMM)

Components

Diodes: zener (10-v)

Resistors: 1K (2pcs), 3.3K

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ZENER DIODE REGULATION

1. Construct the circuit of figure 4. Record the measured value of each resistor.

Figure 4

2. Measure the value of VL and VR. Using the measured values calculate the value for currentacross R, IR, current across RL, IL, and current across zener diode IZ.

3. Change RL to 3.3K and repeat step 2.

4. Comment on the results obtained in step 2 and 3.

V.TABLE/DATA:

1. R(measured)= ________, RL(measured)= _________

2. VR(measured)= ________, VL(measured)= ________

IR=VR/R= ________, IL=VL/RL= ________IZ=IR-IL= ________

3. Change RL to 3.3K

RL(measured)= ________

VR(measured)= ________, VL(measured)= ________

IR=VR/R= ________, IL=VL/RL= ________

IZ=IR-IL= ________

VI.COMPUTATION:

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VII.CONCLUSION:

VIII.QUESTIONS:

1. Design a zener voltage regulator to meet the following specifications:

The input voltage is 24 V dc, the load current is 35 mA, and the load voltage is 8.2 V.

2. In a zener diode regulator, What value of load resistance results in the maximum zener current?

3. How much voltage appears across a zener diode when it is forward-biased?

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EXPERIMENT NO. __

WAVE RECTIFIER

I.OBJECTIVES:

To calculate draw the DC output voltages of half-wave and full-wave rectifiers.


Like the half wave circuit, a full wave rectifier circuit produces an output voltage or current which ispurely DC or has some specified DC component. Full wave rectifiers have some fundamental advantagesover their half wave rectifier counterparts. The average (DC) output voltage is higher than for half wave, theoutput of the full wave rectifier has much less ripple than that of the half wave rectifier producing asmoother output waveform.

In a Full Wave Rectifier circuit two diodes are used, one for each half of the cycle. A transformer is usedwhose secondary winding is split equally into two halves with a common centre tapped connection, Thisconfiguration results in each diode conducting in turn when its anode terminal is positive with respect to thetransformer centre point producing an output during both half-cycles, twice that for the half wave rectifier soit is 100% efficient.


Instrument

DC power supply, Digital mulitmeter (DMM),function generator,oscilloscope

Components

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Diode: Silicon (D1N4002) or equivalent 4pcs.

Resistors: 2.2K,3.3K


Half-Wave Rectification

1. Construct the circuit of figure 5. Set the supply to 9V p-p sinusoidal wave with thefrequency of 1000Hz. Put the oscilloscope at function generator and sketch the inputwaveform obtained.

2. Put the oscilloscope probes across the resistor and sketch the output waveformobtained. Measure and record the DC level of the output voltage using the DMM.

Figure 5.

3. Reverse the diode of circuit of figure 5. Sketch the output waveform across theresistor. Measure and record the DC level of the output voltage.

4. Comment on the results obtained from step 2 and 3.

Full-Wave Rectification

1. Construct the circuit of figure 5-a. Set the supply to 9v p-p with the frequency of1000Hz. Put the oscilloscope probes at function generator and sketch the inputwaveform obtained.

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2. Put the oscilloscope across the resistor and sketch the output waveform obtained.Measure and record the DC level of the output voltage using the DMM.

Figure 5-a

3. Replace diodes D3 and D4 of circuit of figure 5-a by 2.2K. Draw the output waveformacross the resistor. Measure and record the DC level of the output voltage.

V.TABLE/DATA:

Half-Wave Rectification:

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Reverse Diode:

Full Wave Rectification:

Diodes replaced with resistors

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3. For a half-wave rectifier there is current through the load for approximately what percentage of theinput cycle?

4. Describe the operation of a full-wave center-tapped rectifier.

EXPERIMENT NO. 6

CLIPPER CIRCUITS

I.OBJECTIVE:

To calculate and measure the output voltages of clipper circuits.


Clipper or clamping is the one that clamp the signal to a different dc level. The network must havea capacitor, a diode, and a resistive element also known as dc restorer.

III.EXPERIMENTAL PROCEDURE:

Parallel clippers

1. Construct the circuit in figure 6. The input signal is an 8V p-p square wave atfrequency of 1000Hz. Record the resistance value.

2. Set the oscilloscope in DC mode.

3. Put oscilloscope probes at function generator and sketch the input waveform obtained

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Figure 6

4. Sketch the output waveform obtained from the oscilloscope

5. Reverse the battery of the circuit and sketch the output waveform.

6. Change the input signal of the circuit of figure 6. To an 8V p-p sinusoidal signal withthe same frequency of 1000Hz. Repeat step 3 and 4 for this circuit.

Series Clippers

1. Construct the circuit in figure 6-a. The input signal is an 8V p-p square wave atfrequency of 1000Hz. Record the measured resistance value.

2. Set the oscilloscope in DC mode.

3. Put the oscilloscope probes at function generator and sketch the input waveformobtained.

Figure 6-a

4. Sketch the output waveform obtained from the oscilloscope.

5. Reverse the battery of the circuit and sketch the output waveform.

6. Change the input signal of the circuit of figure 6-a to an 8V p-p sinusoidal signal withthe same frequency of 1000Hz Repeat step 3 and 4 for this circuit.

V.TABLE/DATA

Parallel Clippers

Vin square wave

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Series Clippers

Vin, Square-wave

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Vin, Square-wave battery reversed

VI.COMPUTATION:

VII.CONCLUSION:

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I.OBJECTIVE:

To determine the quiescent operating conditions of the fixed bias BJT


Biasing a transistor means to turn on the device or to set the device into active condition, Bipolarjunction transistor refer to the two charged carrier the n-carrier and the p-carrier. BJT is a three terminaldevice namely the emitter, base, collector. Base is always different type of material compared to bothcollector and emitter. Although the emitter and collector are made of the same material, they are notinterchangeable, because they differ in the level of doping. The three terminal can be viewed as emitteremits charged carriers and collectors collect the charged carriers while the amount of charged carriers orcurrent that is emitted by the emitter and collected by the collector is controlled by the base.


Instruments

1 DC power supply

3 Digital Multimeter (DMM)

Components

Resistors

2.7K, 1M

Transistors

2N3904, 2N4401


Fixed-Bias Configuration

1. Measure all resistor values (RB and RC) from circuit in figure 7 using DMM. Record them

2. Construct circuit as of figure 7 using 2N3904 transistor and VCC=20V.

3. Measure the voltages VBE and VRC. Record them.

4. Calculate the resulting base current, IB and collector current, IC using values obtained, Find

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5. Using the values obtained in step 4, calculate the values of VB, VC, VE, and VCE.

6. Energize the network in figure 7, Measure VB, VC, VE, and VCE.

7. How do the measured values (step 6) compare to the calculated values (step 5)?

8. Simply remove the 2N3904 transistor replace with 2N4401 transistor.

9. Then, measure the voltages VBE and VRC. Using the same equation, Calculate the values of IBand IC. From the values obtained, determine the value for 2N4401 transistor.

10. Compile all the data needed for both transistor in table 7-a.

Figure 7

11. Calculate the magnitude (ignore the sign) of the percent change in each quantity due to achange in transistor.

12. Place the results of your calculations in table 7-b.

V.TABLE/DATA:

1. RB(measured)= ________, RC(measured)= ________

2. VBE (measured)= ________, VRC(measured)= ________

3. IB= ________, IC= ________, = ________

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4. VB (calculated) = ________, VC(calculated) = ________

VE (calculated) = ________, VCE(calculated) = ________

Show all your works!

5. VB (measured) = ________, VC (measured) = ________

VE (measured) = ________, VCE (measured) = ________

6. Comparison of results from step 5 and step 6:

7. VBE (measured) = ________, VRC (measured) = ________

IB= ________, IC= ________, = ________

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8.

Transistor type VCE (V) IC (mA) IB (A)

2N3904

2N4401

Table 7-a

9.

10.

% % IC % VCE % IB

Table 7-b

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VI. COMPUTATION

VII. CONCLUSION

VIII. QUESTIONS

1. Based on the configuration of fixed-bias what will happen if the base resistor is decreased to avery small resistance?

2. Discuss why BJT was called a current controlled carrier?

3. How will you set BJT into active region of operation?

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EXPERIMENT NO. 8

JFET CHARACTERISTICS

I.OBJECTIVES:

To establish the output and transfer characteristics for a JFET transistor.

II. BACKGROUND AND INFORMATIONS:

The bipolar junction transistor relies on the two types of charges: free electrons and holes. That iswhy it is called bipolar: the prefix bistands for two on the other hand Field effect transistor (FET). Thistype of transistor is unipolarbecause it depends on only one type of charge, either free electrons or holes.In other words, an FET has majority carrier but not minority carriers. In general, JFETs are moretemperature stable than bipolar transistors. Furthermore JFETs are typically much smaller than bipolartransistors. This size difference makes them particularly suitable for use in ICs, where the size of eachcomponent is very critical.

The depletion layers are actually wider near the top of p-type materials and narrower at the bottom.The reason for the change in the width can be understood by realizing that the drain current I D will produce

a voltage drop along the length of the channel. With respect to the source, a more positive voltage ispresent as you move up the channel toward the drain end. Since the width of a depletion layer isproportional to the amount of reverse-bias voltage, the depletion layer of the p-n junction must be wider atthe top, where the amount of reverse-bias voltage is greater. The pinch off voltage V P is the point at whichfurther increases in VDS are offset by a proportional increase in the channels resistance. This means that ifthe channel resistance is increasing in direct proportion to VDS above VP, ID must remain the same aboveVP.

III. MATERIALS:

Instruments:

DC Power Supply: 9V and 25 VDigital multimeter

Components:Resistors: 10K, 100, 1KPotentiometer: 1M, 10K

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IV. EXPERIMENTAL PROCEDURES:

Part A: Measurement of the saturation current IDSS and pinch-off voltage VP for JFET

1. Referring to below, construct the circuit. The function of 10K resistor in the circuit is to protectthe circuit if the 9v supply is connected with wrong polarity and the potentiometer is sets on itsmaximum value

2. Measure R value.

3. Vary the 1M potentiometer until VGS=0v. Measure ID at this time. (ID=IDSS) When VGS=0V.Record the ID measured.

4. Set VDS to 8V by varying the 10K potentiometer. Measure the voltage across R, V R.

5. Calculate the saturation current, IDSS using the measured resistor R and VR Record IDSScalculated.

6. Maintain VDS at about 8V and reduce VGS until VR drops to 1mV. At this level, ID=VR/R,1mV/100= 10A 0 mA. Record VGS value. The VGS value (when ID is 0mA) is the pinch-offvoltage Vp.

7. Using the values IDSS and VP sketch transfer characteristics for the device using Shockleysequations (given in the result section) plot at least 5 points on the curve (Use VP


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3. Vary the 1M potentiometer until VGS=-1V. Maintaining VGS=-1V, Vary VDS through the levels oftable 5-1 and record the calculated value of ID.

4. Repeat step 3 for the values of VGS in table 5-1. Discontinue the process if VGS exceeds VP.

5. Plot the output characteristics for the JFET.

6. Compare the IDSS and VP values obtained from step 5 with those measured in part A givecomments.

Part C: Transfer characteristics (JFET)

1. Using the data from table 5-1, record the values of ID for the range of VGS at VDS=3V in table 5-2.

2. Repeat step 1 for VDS=6V, 9V and 12V.

3. For each level of VDS, plot ID versus VGS on the graph. Plot each curve carefully and label eachcurve with the values of VDS.

V.TABLE /DATA:

Part A:

2. R (measured)=________

3. IDSS (measured)=________

4. VR (measured)=________

5. IDSS (calculated)=________

IDSS=ID=VR/R

6.VGS (measured)=VP=________

7. ID=IDSS(1-VGS/VP)2

5 Points for plot (calculated)

VGS=0V, ID=IDSS=

VGS=______ ID=______

VGS=______ ID=______

VGS=______ ID=______

VGS=______ ID=______

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VGS=______ ID=______

Note: VP


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Part C: Transfer Characteristics (JFET)

1.

VDS(V) 2 3 9 12

VGS (V) ID(mA)

-0.0

-0.5

-1.0

-1.5

-2.0

-2.5

2. Plot of ID vs VGS

VI. COMPUTATION:

VII. CONCLUSION:

VIII. QUESTIONS:

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1. When a JFET is cut off, the depletion layers are?

2. When the gate voltage becomes more negative in an n-channel JFET, the channelbetween the depletion layer_________________

Documents

Elecs1 Lab-manual 2003