LIC & Communication Lab Manual LIC & COMMUNICATION LAB MANUAL FOR V SEMESTER B.E (E& ( E&C) (For private circulation only) NAME: DEPARTMENT OF ELECTRONICS & COMMUNICATION SRI SIDDHARTHA INSTITUTE OF TECHNOLOGY (A Constituent College of Sri Siddhartha university) MARLUR, TUMKUR-572105
LIC & Communication Lab Manual CONTENTS LIC: 1. Schmitt Trigger Design and test a Schmitt trigger circuit for the given values of UTP and LTP 2. Design and test R-2R DAC using op-amp 3. Design and test the following circuits using IC 555 a. Astable multivibrator for given frequency and duty cycle b. Monostable multivibrator for given pulse width W 4. Precision rectifiers both Full Wave and Half Wave COMMUNICATION: 5. II-Order Low Pass and High Pass Active Filters 6. II Order Active Band Pass Filter. 7. Attenuators 8. Class-C C Tuned Amplifier 9. Amplitude modulation using transistor/fet (Generation and detection) 10. Pulse Amplitude Modulation 11. Pulse Width Modulation & Pulse Position Modulation 12. Frequency modulation using 8038/2206 13. Pre & De Emphasis Networks 14. Transistor Mixer
LIC & Communication Lab Manual Testing Of Equipments before Starting the Conduction (Check List) 1. OP AMP Apply sine wave of amplitude 1 volt (1 khz) as shown in ckt diagram, if IC is functioning the output will be a square wave with peaks at + V SAT and Vsat. 2. 555 Timer : If IC is good for the applied 5 V D.C supply to pin no.8 then the voltage at pin no. 5 will be 2/3 Vcc (3.3 Volts) 3. Transistor Identify emitter, base and collector of the transistor, with DMM in diode position, if transistor junctions are good it indicates a low resistance upon forward biasing emitter base junction or collector base junction and indicates either OL or 1.(depending on DMM) upon reverse biasing EB or CB junctions. 4. Source impedance i of ASG: 1. Connect the DRB across ASG as shown in the fig keeping all the knobs at maximum resistance position. 2. Adjust the amplitude of sine wave of 5V pp at 1 KHz. 3. Start reducing the resistance of DRB this inturn reduces the output voltage also. 4. Continue step 3 till output signal is half of the initial value. (2.5 V pp) 5. Source resistance Rs is that value of DRB resistance when the amplitude reduces to 2.5V
LIC & Communication Lab Manual
Circuit Diagram: Circuit diagram of Schmitt trigger for design example (1) V o volts Y- axis - X-axis X-axis - V o volts -Y axis Transfer Characteristics (With +Ve V R ) 1
Experiment No: 1 DATE: / / SCHMITT TRIGGER Aim: To design and test Schmitt trigger circuit for a given value of UTP and LTP points. Procedure: 1. Schmitt trigger is designed for the given UTP and LTP. 2. Circuit connections are made as shown in fig 1 3. Sinusoidal input signal of amplitude (larger than the UTP & LTP) is applied at the input of Schmitt trigger. 4. Output voltage V 0 is observed on CRO. The Transfer characteristic is observed and UTP and LTP are measured and compared with designed values. Result: UTP (THEORITICAL) LTP (THEORITICAL) UTP (PRACTICAL) LTP (PRACTICAL) 2
Design: V UTP = 6V, V LTP = -2V V UTP = 6V = R1V REF R + R 1 2 R2V SAT + R + R 1 2 V LTP = -2V = R1V REF R + R 1 2 R2VSAT R + R 1 2 2V REF R 1 V UTP + V LTP = 4 = => R 1 +R 2 2V SAT R 2 V UTP - V LTP = 8 = = -------------------------- (2) R 1 +R 2 Therefore V R = 3V, assume R 2 = 1kΩ => R 1 = 2kΩ T V i +βv SAT V m UTP Volts - β V SAT LTP time + V SAT V o Volts time - V SAT Input- Output Waveforms (With V r = 0) 3
Conclusion: Result: Staff Incharge Assignments: 1. Define UTP, LTP & hystrisis loop. 2. Application of Schmitt trigger. 4
Circuit Diagram: Digital i/ps from switch box Design: Vo= 5V, Circuit diagram of R-2R DAC V ref V out = X (D 0 + 2D 1 + 4D 2 + 8D 3 ) 16 Let R = 5k & 2R = 10k, Typical Converter Relationship:- V out (Full scale) Gain error V out Resolution or 1 LSB Offset error 0FH Digital i/p Typical Converter Relationship 5
Experiment No: 2 / / DATE: DAC USING R-2R LADDER NETWORK Aim: To Design and Test R-2R DAC using op-amp. Procedure: 1. Connections are made as shown in the fig 1. 2. The digital inputs are connected from switch box. The 4 bits are increased in steps from 0000 to 1111 and at each step output voltage V 0 is measured using multimeter. The readings are tabulated and verified against the theoretical output. 3. Graph of digital inputs v/s analog output is plotted, and different parameters are as shown in fig 2 are determined and recorded. Tabular Column: b 3 b 2 b 1 b 0 V out (Theoretical) Volts V out (Practical) Volts 0 0 0 0 0 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 0 1 0 1 0 1 1 0 0 1 1 1 1 0 0 0 1 0 0 1 1 0 1 0 1 0 1 1 1 1 0 0 1 1 0 1 1 1 1 0 1 1 1 1 Conclusion: Result: 1. LSB or Resolution = Volts 2. Offset error = Volts 3. V out (full scale) designed = Volts 4. V out (full scale) obtained = Volts 5. Gain error = Volts Assignment: 1) Explain the working of R-2R digital to analog circuit? Staff Incharge 6
2) Define Resolution.? A) Circuit of Astable Multivibrator Waveforms of Astable Multivibrator 5V Y V o volts time 2/3 V cc V c (volts) 1/3 V cc T 1 T 2 time Design 1: To Design an Astable multivibrator circuit using 555 timer for f = 1 KHz, duty cycle = 70 % and V out = 5 Volts. We Know that T 1 = 0.69 R A C T 2 = 0.69 R B C and Duty Cycle = Given duty cycle= 70 % R A + R B 70 = = 0. 7 R + 2R 100 A B T1 T + T 1 2 R = R A A + R + 2R B B 7
Experiment No: 3 / / DATE: ASTABLE & MONOSTABLE MULTIVIBRATOR AIM: To design and test Astable and Monostable Multivibrator for the given specifications using timer IC 555. PROCEDURE:- I. Astable Multivibrators ( AMVs) 1. Circuit is rigged up as shown in the circuit of figure (1) and the power supply is Switched ON. 2. The output voltage waveform and the voltage across the timing capacitor are Observed using a CRO. 3. All the relevant voltage levels like 1/3 Vcc, 2/3 Vcc are noted. T 1 and T 2 are also measured and noted. The frequency of oscillation and the duty cycle are calculated and verified against the designed values. 4. The above procedure is repeated for the circuit shown in figure (2) for any duty cycle. 5. Circuit is designed & tested for the specifications given in exercise (1). II. Monostable Multivibrators ( MMVs) 1. Rigup the circuit as shown in the figure, switch on the power supply. 2. Apply the trigger signal using signal generator at pin no.2 (adjust the duty cycle of trigger pulses so that its off time is less than pulse width W) 3. Observe the output signal at pin no.3 4. Capacitor voltage is observed and voltages are measured and verified. 8
or R A + R B = 0.7 R A + 1.4 R B 0.3 R A = 0.4 R B R A = 1.33 R B for R B = 1 k Ω, R A = 1.33 k Ω T = T 1 + T 2 & T = 0.69 (R A + 2R B ) C Given f = 1 KHz, therefore T = 1msec 1ms = 0.69 [1.33 K + (2 x 1 K)] x C Therefore C = 0.44 µf (Use two numbers of 0.22 µf in parallel) B) Circuit of Monostable multivibrator circuit using 555 timer IC +5 V IN4001 4 8 R 1 R 1 kω C 1 = 0.1 µf 3 o/p 2 trigger from Pulse Gen 7 6 C 1 5 0.01 µf Waveforms in a Monostable Multivibrator V trig 5V Trigger 0 time V 0 (V) 2/3V cc V C (V) S S Q S t p time time 9
Design: Ton = 1ms (given) Ton = 1.1Rc Assume C = 0.1µF 1x10-3 1.1 R = 0.1x10-6 R = 9.09 kω, use standard value = 10 kω Gnd 1 8 V cc Trigger 2 7 Discharge Output 3 6 Threshold Reset 4 5 Control V g Fig (a) : PIN DIAGRAM OF 555 timer Note: - In the circuit diagrams that follow, only pin numbers are marked. Referring to the pin diagram of Fig (a), specify the pin functions accordingly for all the circuit diagrams. Conclusion: Result: Assignment: 1. What are multivibrators? 2. Classifications of multivibrators. 3. Mention any two applications of Astable multivibrator? 4. Define stable and quasi stable states. Staff Incharge 10
a) Half Wave Precision Rectifier: (R a ) 10 KΩ D 2 IN4001 ASG (R b ) 1KΩ V i = 0.2 v +V CC D B A IN4001 f i = 1 KHz -V CC V O to CRO Fig (1):- Circuit Diagram of half wave rectifier circuit. Waveform: V i Volts V m t V o D 2 on D 1 on D 2 on Volts D 1 off D 2 off D1 off t Transfer Characteristics: V o V i V i Transfer Characteristics Fig (1a): Waveforms & Transfer Curve 11
Experiment No: 4 / / DATE: PRECISION RECTIFIERS Aim: To Rig Up And Test Half Wave and Full Wave Precision Rectifiers. Apparatus Required: IC741, Diodes, Resistors, ASG and probes, Base Board, Adopters & CRO, Digital Multimeter (DMM) & Probes, Connecting wires and Power supply. Procedure: 1. Connections are made as shown in the circuit of fig 1. 2. A signal generator is connected to the input. A sinusoidal input voltage of amplitude less than 0.7 V with frequency of 1 KHz is applied and the input and output waveforms at points A & B are observed on CRO. 3. The CRO is then set to X-Y mode and its transfer characteristics are observed. 4. The values of R a and / or R b are changed and change in the slope of transfer curve is observed. 5. The minimum input voltage, which can be rectified, is measured. 6. The step 2 to 5 is repeated for full wave rectifier circuits shown in fig 2. Conclusion: Result: Staff Incharge Assignments: 1. What are precision rectifiers? 2. Explain how cut in voltage is overcome in precision rectifiers? 12
Design: Given A = 5 0.5 = 10 = R a R Assume R = 1KΩ Ra = Rb = 10KΩ The above design is applicable to half wave, full wave (positive precision & negative precision) rectifier. b) Full Wave Precision Rectifier Circuit Diagram (Positive Full Wave Rectifier Circuit): (R a ) 10 k Ω 10 k Ω 10 kω +Vcc 1 kω IN4001 +Vcc f I = 1KHz V I = 0.2v ASG IN4001 V O to CRO -V CC -V CC Waveform: (R b ) 10 KΩ V i Volts V m t V o Volts t Waveforms & Transfer Curve V i -V I(max) V I (max) V 13
Circuit Diagram (Negative Full wave Rectifier Circuit): (R a ) 10 k Ω 10 k Ω 10 kω R=1KΩ +Vcc IN4001 +Vcc F in =1 KHz Vin = 0.2 V IN4001 V 0 ASG -V CC -V CC Waveform: R b Use Ra=Rb= 10 KΩ initially V m V i Volts t V o Volts t Waveforms & Transfer Curve V o V i -V I(max) V I (max) V i 14
CIRCUIT DIAGRAM: - II-Order Active Low Pass Filter II-Order Active High Pas7s s Filter Design:- (LPF & HPF) Assume Pass band gain AV A = 2, Cutoff frequency fc f = 5KHz Rf 1. Amplifier: AV A = 1 + = 2, then Rf = R, choose Rf = R = 10KΩ R 2. Filter Circuit : Cut off frequency fc f = 1 2πR C 1 1 = 5KHz Choose C1 C = 0.01µf f then R1 R = 3.183 KΩ 3.3 KΩ 15
Rf = 10KΩ, R1 R = 3.3KΩ, C1 C = 0.01µf, Op-amp = µa741 Experiment No: 5 / / DATE: II Order Low Pass and High Pass Active Filters AIM: - Design a second order Butterworth active low pass / high pass filter for a given cut-off frequency fc = Hz. Conduct an experiment to draw frequency response and verify the roll off. PROCEDURE: - 1. Connections are made as shown in the circuit diagram. 2. Apply sine wave i/p signal of peak amplitude 5 volts. 3. Check the gain of non-inverting amplifier by keeping the frequency of the input signal in the pass band of the filter. Note down the output voltage VO max. 4. Keeping the input signal amplitude constant, vary the frequency until the output voltage reduces to 0.707 Vo max, the corresponding frequency is the cut-off frequency (fc) of the filter. To find the Roll oll-off off factor :- 1. For LPF :- Keeping the input signal amplitude constant, adjust the input frequency at 10fC. Note down the output signal amplitude. The difference in the gain of the filter at fc and 10fC gives the Roll-of factor. 2. For HPF :- Keeping the input signal amplitude constant, adjust the input frequency at 0.1fC, note down the output signal amplitude. The difference in the gain of the filter at fc and 0.1fC gives the Roll-of factor. 16
Tabulation: High Pass Filter I/P frequency in i Hz O/P Voltage VO V O P P (volts) O P- Vi i p-p p = Volts (Constant) Gain magnitude Gain magnitude in DB (Vo/Vi) 20log(Vo/Vi) Roll off = - (G1 - G2) db/decade = Note: The values of G1, G2 are determined from the Tabular Column over a frequency range of 1 Decade. Frequency Response for High Pass Filter 17
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Tabulation: Low Pass Filter I/P frequency in Hz O/P Voltage VO V O P P (volts) O P- Volts (Constant) Gain magnitude Gain magnitude in DB (Vo/Vi) 20log(Vo/Vi) Vi i p-p p = Roll off = - (G1 - G2) db/decade = Note: The values of G1, G2 are determined from the Tabular Column over a frequency range of 1 Decade. Frequency Response for Low Pass Filter Conclusion: Result: Assignment Staff Incharge 1. What are filters? 3. Compare Active and passive filters. 2. List the type of filters? 4. Define low pass & high pass filters. 19
CIRCUIT DIAGRAM: - II-Order Active Band Pass Filter Design: Specifications: Pass band gain AV = 1.586, cut -off frequency fh = 5 KHz, fl=8 KHz, BW= 3 KHz 1. Amplifier: Voltage gain AV = 1 + Rf / R = 1.586, choose R = 10KΩ, Then Rf = 5.86 kω (use 5.6 kω+ 220 Ω std value) 2. Filter: Cut - off frequency fh= 1/2π R2C2= 5 KHz, Choose C2= 0.01µf, then R2 = 3.183 kω (Select R2 = 3.3 kω) Cut - off frequency fl = 1/2π R1 C1 = 8 k Hz, Choose C1= 0.01µf, then R1= 1.989 k Ω (Select R1 = (1.5 kω + 470Ω)) 20
Experiment No: 6 / / DATE: II Order Band Pass Active Filters AIM: - Design a second order band pass and band stop active filter for a given frequencies fc1 = Hz and fc2 = Hz. Conduct an experiment to draw frequency response and verify the Roll off (Band Width = 3 to 5 KHz). PROCEDURE: - 1. Connections are made as shown in the circuit diagram. 2. Apply sine wave i/p signal of peak amplitude 5 volts. 3. Check the gain of non-inverting amplifier by keeping the frequency of the input signal in the pass band of the filter. Note down the output voltage VO max. 4. Keeping the input signal amplitude constant, vary the frequency on either side of pass band until the output voltage reduces to 0.707 Vo max, the corresponding frequencies are the lower cut-off frequency (fl) and the upper cut-off frequency (fh) of the filter. To find the Roll oll-off off factor :- 1. For LPF :- Keeping the input signal amplitude constant, adjust the input frequency at 10fC, note down the output signal amplitude. The difference in the gain of the filter at fc and 10fC gives the Roll-of factor. 2. For HPF :- Keeping the input signal amplitude constant, adjust the input frequency at 0.1fC, note down the output signal amplitude. The difference in the gain of the filter at fc and 0.1fC gives the Roll-of factor. 21
Tabulation: Band Pass Filter Frequency Hz Vi i p-p p = O/P Voltage VO V PP (volts) O PP Volts (Constant) Gain in DB Gain (Vo/Vi) 20 log (Vo/Vi) 22
Frequency Response for Band Pass Filter Conclusion: Result: Staff Incharge Assignments: 1. Define a) BPF b) BEF c) Roll off 23
d) Bandwidth e) Stop band f) Pass band CIRCUIT DIAGRAM: - T-Type Type Attenuator π-type Attenuator 24
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