electronics circuit design lab

ELECTRONIC CIRCUIT DESIGN [EC-683]Saroj Mohan Institute Of Technology (Degree Div)Electronics and Communication Engineering 3rd year 2nd semester, 2009-2010.

Electronic Circuit Design| Lab Report

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Without the permission & help of our teachers it is impossible for us to do this Seasonal lab in electronics circuit design. This lab gives us the opportunity to gather very interesting & technical knowledge based on electronic circuit, design parameters and its components. We hope that this lab will be very helpful to us in our future, as we are students of Electronics & Communication Engineering.

Further we express our heartfelt thanks to Samir Sir and Sayan Sir to provide us with the essentials for this lab from the very beginning. They also give us so many technical & practical knowledge on electronics system & electronic circuit components.

It is undeniable that without the help of our other group members it will be very hard to perform this lab, so we are grateful to our group mates also.

Name SOURAV DHAR SUDIP KUMAR PAL DEBAYAN CHAKRABORTY DEBASISH KUMAR BIT

Roll no. 071680103001 071680103013 071680103019 071680103033


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INDEX

SL NO. 1

ASSIGNMENT NAME Design a DC power Supply

DATE

PAGE 4-10

REMARKS

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Design a square wave generator for 650 Hz with the help of an astable multivibrator using NE555 IC Design an audio frequency amplifier for the gain of 60dB To design a transistor amplifier Design a monostable multivibrator using NE555 IC To design Full Subtractor using Multiplexer. DATASHEETS of components used

11-15

16-21

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22-24

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25-26

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27-29

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ASSIGNMENT NO.-1 Assignment Name:-Design 12V regulated power supply to have a maximum current of 500mA. Theory:There are many type of power supply. Most are design to convent high voltage AC mains electricity to a suitable low voltage supply for electronic circuit &other devices. For example, a 5v regulated power supply

Block diagram of a Reguleted power system Power supplies made from these blockes are deseribed below:1. Transformer only. 2. rectifier. 3. smoother. 4. regulator. BLOCK DIAGRAM:::---


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Transformar : : An input voltage of 220 volt a.c is applied to the transformer. The transformer steps down high voltage AC mains to low voltage AC. Transformers convert AC electricity from one voltage to another(220 volt to 6 volt)with little loss of power. Rectifier: A rectifier is an electrical device that converts alternating current (AC) to direct current (DC), and the process is known as rectification Smoothimg: Smoothing is performed by a large value electrolytic capacitor connected across the DC supply to act as a reservoir, supplying current to the output when the varying DC voltage from the rectifier is falling. The diagram shows the unsmoothed varying DC (dotted line) and the smoothed DC (solid line). The capacitor charges quickly near the peak of the varying DC, and then discharges as it supplies current to the output.

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Regulator: A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level and the process is called regulation. Electronic Circuit Design| Lab Report 6

Standard circuit:--Full wave rectifier circuit::--

COMPENT REQUIRED:1.220V/18-0-18 1 Ampere centre- tapped transformer. 2. Vero board. 3. Diodes. 4. Capacitor. 5. C.R. O 6. Patch cord.

SPECIFICATION:1. FULL-WAVE RECTIFIERS:- This is a classic circuit that can accurately convert an AC signal to DC. At 40 Hz the input signal can be as low as 0.05volts peak to peak. 2. Full wave rectifier operates to 200MHz:- This circuit used current feedback amplifiers to implement a wideband full wave rectifier for application such as Control /AGC system reference or as amplitude indicator.

3. Full wave Rectifier uses Current feedback amplifier:Doubling for rectifying or continuous wave signal by using diode bridges usually causes problems with low input or at high frequency. Electronic Circuit Design| Lab Report 7

CALCULATION:-(Without Filter)--

The Ripple factor of a full wave rectifier is given by=( (VrmsVdc)2-1) Vdc=1/0Vmsintd(t) =Vm/[-cos(t)]0 Idc=Vdc/RL=2Vm/RL=2Im/ Irms=Im/2 The Rms value of the voltage at the load resistance is Vrms=[1/0Vm2sin2td(t)]1/2 =Vm/2 =(Vm/22/(2Vm/)2-1) =(/2)2-1 =0.482 Effiency is the ratio of DC output power to AC input power =(DC o/p power)/(AC i/p power) =Pdc/Pac = (Vdc2/Rl)(Vrms2/Rl) =[2Vm/]2/[Vm/2]2 Electronic Circuit Design| Lab Report 8

=8/2=81.2% So the maximum efficiency of full wave rectifier is 81.2% .Transformer utilization factor(TUF)is used to determine the rating of a transformer secondary. It is determine by considering the primary and the secondary winding separately and it gives a value of 0.693. Form factor is defined as the ratio of the rms value of the output voltage to the average value of the output voltage. Form factor=((rms value of o/p voltage)/(avg value of the o/p voltage) =(Vm/2)/(2Vm/2) =/22 =1.11 The peak factor is defined as the ratio of the peak value of the output voltage to the rms value of the output voltage Peak factor=(peak value of0/p voltage)/ (rms value of0/p voltage) =Vm/(Vm/2) =2 Peak inverse voltage for full wave rectifier is 2Vm because the entire secondary voltage appears across the non-conducting diode (WITH FILTER:::---)

Ripple Voltage Triangular wave form The charge it has acquired=Vrp p*C Electronic Circuit Design| Lab Report 9

The charge it has lost=Idc * T2 (Vrp p *C) = (Idc *T2) If the value of the capacitor is fairly large, or the value of the load resistance is very large, then it can be assumed that the time T2 is equal to half the periodic time of wave form. T2=T/2=1/2f Then Vrp p=Idc/2fc From the above assumption the ripple wave form will be triangular and its rms value is given by Vrms=(Vrp p)/ 23=(Idc/(43fcRL)=(Vdc)/( 43fcRL) So,Idc=Vdc/RL Ripple y=Vrms/Vdc=1/43fcRL, Idc= Vdc/RL APPROXIMATION::-LOAD RESISTENCEr=2 k ohoms. Load capacitanceC=10F RESULT:


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FIG: WITHOUT FILTER

FIG: WITH FILTER TESTING:-1.

Consider the first half cycle .When the source voltage polarity is positive(+) on top and negative(-)on the bottom. At this time only the top diode is conducting .The bottom diode in blocking current ,and the load sees the first half of the sine Electronic Circuit Design| Lab Report 11

wave. Positive on the top and negative on the bottom. At this time only the top diode is conducting. Only the top half of the transformers winding carries current during this half cycle. 2.

During the next half cycle ,the AC polarity reverses .Now the other diode and the other half of the transformer secondary winding carry current while the portions of the current formely carrying current during the last half cycle. The load still sees half of the sine wave of the same polarity as before; positive on top & negative on bottom. Conclusion:-

Rectification is the conversion of alternating current (Ac) direct current (Dc). A full wave in a circuit that converts both half cycle of AC voltage waveform to an unbroken series of voltage pulses of the same polarity. The resulting DC delivered to the load doesnt pulsate as much, so this are the thing we conclude at the end.


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ASSIGNMENT NO - 02

AIM: - Design a square wave generator by using Astable Multivibrator. THEORY:-

555 Timer:-

The 8-pin 555 timer must be one of the most useful that is ever made and is used in many The input of the 555-timer as follows:1) TRIGGER INPUT: - when 2M. 2) THRESOLD INPUT: - When >2/3V3 (active high) this makes the output low, it monitors the charging of the timing capacitor in astable & monostable circuits. It has a high input impedance >10M . 3) RESET INPUT:- When it is less than 0.7V(active low) this makes the output low (..). Overriding the other inputs when not required, it should be connected to +Vs. It has an input impedance of about 10K . 4) CONTROL INPUT:- This can be used to adjust the threshold voltage which is set internally to be 2/3Vs. Usally this function is not required and the control Electronic Circuit Design| Lab Report 13

input is connected to ..0v with a 0.01f capacitor to eliminate electrical noise.

COMPONEMTS REQUIRED:1) 555 Timer IC 2) Two resistors 3) Two capacitors 4) Diode 5) C.R.O

OPERATION PERFORMED:-

With the output high (+Vs), the capacitors CI is charged by current flowing through R1 & R2, the threshold and trigger input monitor the capacitor voltage and when it reaches 2/3Vs (threshold voltage) the output becomes low and the discharge pin is connected to 0V. The capacitor now discharges with current flowing through R2 into the discharge pin. When the voltage fails to 1/3Vs (trigger voltage) the output becomes high again and the discharge pin disconnected, following the capacitors to start charging again. This cycle repeats continuously unless the reset input is connected to 0V which forces the output low while reset is 0V.


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DUTY CYCLE:-

90% duty cycle (Tm =4Ts)

Ts= 0.7*R2*C1 Duty cycle with diode = Tm/ (Ts+Tm) = R1/ (R1+R2)

DESIGN:Vcc 4 RA 7 RB 6 2 C 8

555Discharge Threshold Trigger 1

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Output

5 C = 0.1f

Control Voltage

(optional)

Figure 2. The Basic 555 Astable Circuit

DESIGN CONCIDERATION:-

1) Choose C1 to suit the frequency range we require. 2) Choose R2 to give the frequency (f) we require. Assume that R1 is much smaller than R2. 3) R2=0.7/(f*C1) 4) Choose R1 to be about a tenth of R2 (1K min) unless we went to mark time. CALCULATION:1) To calculate the frequency :F=1/0.693*(R1+R2)*C (in H2) 2) To calculate the on time:Ton= 0.693*(R1+R2)*C (in seconds) 3) To calculate the OFF time:TOFF= [0.693*R2*c] 4) To calculate the percent time high (%) :Duty cycle= (R1+R2)/ (R1+2R2) 100% 5) To calculate the percent time low (%):=R2/ (R1+2R2) 100%

Value Value of of R1( R2() )1000 1000 1000 10000 10000 10000 10000 100000

Valu e of C1( F)0.001 0.01 0.1 0.001

Output time High (Second s)0.000007 629 0.000076 0.00076 0.000076

Output time Low (Second s)0.0000069 2 0.000069 0.00069 0.000069

Output Period(High + Low) (Seconds)0.0000014552 0.000145 0.00145 0.000145

Output Output Frequen Duty cy (Hz) Cycle (%)68714.35 6871.43 687.143 6871.435 52.3809 52.3809 52.3809 52.3809


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10000 10000

100000 100000

0.01 0.1

0.000762 3 0.007623

0.000692 0.00692

0.0014553 0.014553

687.1435 68.71435

52.3809 53.3809

APPROXIMATIONS:555 Astable Frequency.

555 ASTABLE FREQUENCIESC1 R2=10K R1=1K 0.001F 0.01F 0.1F 1F 10F

R2=100K R1=10K 6.8KHz 680Hz 68Hz 6.8Hz 0.68Hz

R2=1 R1=100K 680Hz 68Hz 6.8Hz 0.68Hz 0.068Hz

68KHz 6.8KHz 680Hz 68Hz 6.8Hz

TESTING AND RESULTS:A timing interval starts when trigger input (fr) goes lower than 1/3 Vin or 3.33V. When this happens, the 555 output goes high, and the 555 waits for the threshold input (th) to reach 2/3V or 6.67V. As the capacitor a charge, the threshold input slowly raises until it reaches the required level. Then the timing interval ends. The output goes low, and the capacitor is discharging through the dis input. When the capacitor is discharged enough so that the trigger reaches 3.33V, then a new timing interval begins. The end result is a square wave. Electronic Circuit Design| Lab Report 17

CONCLUSION:-

The 555 timer Ic is non figured to be as an astable multivibrator. As astable multivibrator is a timing circuit whose low and high both states are unstable. As such, the output of an astable multivibrator toggle between low and high continuously, in effect generates a train of pulses. The circuit is therefore called pulse generator circuit.

ASSIGNMENT NO - 03 AIM:- Design a single stage audio frequency voltage amplifiers with BJT for a given Av. Zin ,Zout and maximum symmetric output swing. THEORY:The term amplifier refers to any device that increases the amplitude of a signal usually Measured in voltage or current. Especially in audio technology, a wide range of amplifier can be Produced based on product specifications. Transistors are the most important part of amplifier Circuits, capable of controlling at output signal in comparison to an input signal. A transistor can Produce gain. In other words, the transistors are responsible for amplification component of audio amplifier. Class B amplifier are generally used in synchronization. Class B push- pull


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Class AB is more efficient them class A with lower distortion than class B. Another popular method of controlling amplifier distortion in negative feedback. A portion of the Amplifiers output is transferred back to the input. At very high frequency, the gain becomes inversely related to frequency as performance drop off. This continues until the point that the gain drops with an increase in frequency. This input is known as 3 dB point. For optimal performance, the 3dB point of an amplifier should full beyond the amps active range of frequency.

DESIGN:-


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Fig:

OUTPUT STAGE

DESIGN SPECIFICATION:The design specifications are as follows:1) Our amplifier had to be able to amplify a signal from a portable music player (0.8V-1.1V supply voltage load). In order to reach satisfactory amplitude. 1.7 times gain is necessary for each section of the input stage. 2) Class A designs are capable of this gain, and their high inefficiency was not a major factor in the small scale of our experiment. However, these amplifiers invert the input signal. The designer need to increase the power gain in order to drive the speakers at this output. Class AB amplifier are capable of producing power gain. Audio signals in the modern music industry are now broadcast almost exclusively in stereo-sound. To account for the dual signal amplification the entire circuit was repeated. The final output of the amplifier was fed through a low power audio speaker, complete the circuit. TESTING:There are three stages of our audio amplifier are as follows:First stage of audio Amplifier:-

The complicated set-up of the emitter leads to a new equation for determining the resistance.


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A=*RL1 / [R+REL] Re1 Second stage of audio amplifier:-

where, A= gain 400 RL1= sum of resistor in parallel R =*Vt/Ic

The ideal voltage entering the base of the transistor was 3v. The current increasing from 1 amp in the first class A amplifier to 5A in the second. Even through this will result in different resistors values, the equations involved in the calculating are the same in both resistance. Output stage of our amplifier:-


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CALCUCATION:After the circuit was biased, we discovered the certain resistors required for our circuit are arranged in table as follows:-

Theoretical resistor value 5K 180 1.1 280

Actual resistor value 4.7K 200K 1.2K 270

APPROXIMATION:The comparison of the theoretical simulated and actual values at different stage of amplifier is as follows:-


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Voltage V b1 VE1 VC1 VB2 VE2 VC2 VB3 VE3 VE4 VE5

Theoretical 2.86V 2.16V 7.3V 2.86V 2.16V 7V 6V 6.7V 5.3V 6V

Simulated 2.84V 2.18V 7.77V 2.77V 2.07V 7.64V 6.01V 6.57V 6.46V 6.03V

Actual 2.84V 2.16V 7.78V 2.75V 2.04V 7.68V 5.83V 6.57V 5.33V 5.95V

V 0.02V 0.00V 0.48V 0.11V 0.12V 0.69V 0.17V 0.13V 0.03V 0.05V

The comparison of the theoretical, simulated and actual given values of each stage of amplifier:Stage 1 stagest

Theoretical 1.7 1.7

Simulated 1.55 1.65

Actual 1.56 1.56

Gain 0.14 0.14

2nd stage

Final 3.0 2.21 2.14 0.86 Output RESULTS:The computer simulation play an important role in the process of building an audio amplifier:-


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1) 2) 3) 4)

Time domains simulations as:First stage Second stage Output/Third stage Input Signal.

CONCLUSION:In our research, we observed that charging the value of the capacitor in the negative feedback, loop alters the 3dB inversely charging the value of resistors in the circuit can also alter the gain. Overall, the impact on the gain, but it was not enough to prevent the amplifier from operating. We used the exact resistor value, the gain produced was acceptable for our experiment and proved that we can simplify sound.


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ASSIGNMENT NO:-4

AIM:- To design a transistor amplifier . THEORY:-

An amplifier with or without negative feedback having the greatest fidelity in faithfully reproducing the input with the least distortion. Its however the least efficient, in as much as the power delivered to the load is only a small percentage of d.c. power used up in the amplification process. The transistor amplifier must have the three characteristic mentioned below:1) Feedback:- This is where part of output signal is feedback to the input, but 180o out of phase. If it were in phase feedback that we would have an oscillator. 2) Fidelity:- This means many things to many people but to us it means the output must be an exact replica of the input but only magnified or amplified. 3) Efficiency:- The theoretical limit to this amplifiers efficiency is 50% meaning of every watt output. We will use up at least 2 watts of d.c power input to the amplifier.

DESIGN:-


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Fig1: Dc and Ac model A.C only model

Fig2 : Equivalent

DESIGN CONSIDERATION:-

The design specifications are evaluated with SPICE based simulator. Results varied between the simulation and prototype measurements are as follows:1) 24% variation in efficiency. 2) 3% variation in amplifiers dc power dissipation. 3) 31% variation in BJT power requirements. The components required as follows:1) 2) 3) 4) Resistors Transistors Capacitors Power supply

CALCULATION:Base voltage=[R2/(R1+R2)]*12v e.g for 82k for R1 and 39k for R2 Base voltage=[39k/(82k+39k)]*12v= 3.78v Electronic Circuit Design| Lab Report 26

Current through the base resistors. Ib = 12/(R1+R2)=12/(39k+82k)=0.1 mA We have a base voltage of 3.87v and if 0.65v higher than the emitter then the emitter is is (3.87-0.65) which is 3.22v. Rc = 3.22/0.0007v= 4600 APPROXIMATION:The following approximations are required:1) Id= It is a silicon N PN general purpose type 2) d= 0.5w i.e. capable of dissipating 500 mw. 3) VCE = 40 V i.e. dont use if above 20v dc supply. 4) Ic = 0.8A i.e. maximum collector current in 800mA. 5) Hfe = 100 i.e. amplification factor is 100. TESTING:In a transistor amplifier, we have two totally different set of condition. One set are d.c condition and the other set are a.c or R.f conditions. In the d.c conditions, the transistor amplifiers are turned on or have the base opened. To do this, the base have to voltage applied to it which is approximately 0.65v higher than the voltage amplifier at the emitter. In fact, using the property, allows a transistor to be used as a simple switch. Bitter still, arranging about 20000.000 of them at the right way around and get a Pentium. RESULTS:The resulting circuit for transistor amplifier is shown below:-


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The bandwidth increase with the increase of frequency of signal and the bandwidth decreases with decrease in frequency.

CONCLUSION:So, we conclude that transistor is mainly used as current amplifier, the current amplifier is a device that is used to increase the amplitude of current in the signal.

ASSIGNMENT NO:-5 ASSIGNMENT NAME : To Design A Monostable Multivibrator Using 555 IC.


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THEORY:

A monostable circuit produces a single output pulse when triggered.

It is called monostable because it is stable in just one state; i.e. the output low. The output high state is temporary.

CIRCUIT DIAGRAM:

Fig1: 555 Timer ic

Fig2: Simplified circuit of monostable 555 timer

OPERATION:i) The timing period is triggered (started) when the trigger input (555 pin2) is less than 1/3 Vs, this makes the output high (+Vs) and the capacitor C1 starts to change through resistor R1. Once the time period has starter further triggering pulses are ignored. The threshold input (555 pin 6) monitors the voltage across C1 and when this reaches 2/3 Vs the time period is over and the output becomes low. At the same time the discharge (555 pin 7) is connected to 0 volt, discharging the capacitor ready for next trigger. The reset input (555 pin 4) overrides all other inputs and the timing may be calculated at any time by connecting the reset to 0V. This instantly makes the output low and discharges the capacitor. If the reset function is not required, the RESET pin should be connected to +V5, as for our experiment.

ii)

iii)

CALCULATION & OUTPUT:


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The duration of the pulse is called the time period (T). This is determined by resistor R1 and capacitor C1. Time Period T=1.1*R1*C1 T= time period in second(s); R1= resistance in ohm C1= capacitance in farads (F); Here 1.1 coefficient comes because the capacitor charges to 2/3Vs= 67%. So it is a bit longer than the time constant (R1*C1) which is the time taken to charge to 63%. First we have to choose C1 as there are relatively small numbers of values available. Then we choose R1 to have the time period we need. R1 should be in range of 1K ohm to 1u ohm, so we have to use a fixed resister of at least 1k ohm in series if R1 is variable.

APPROXIMATION: As we know, the practical values of the capacitors onelimited. So a particularly selected time period, we may have theoretically calculated values of R1 & C1, but those may not be available in market. So, we have to choose from the nearest value available.

TESTING & RESULT: After completing the circuit, we give the supply (+Vcc) andground (0v) and apply a -ve pulse to the pin2 of the IC. Then we get +ve output from pin3 with respect to ground (0v). We can see the output wave form in CRO. The distortion in the output is due to circuit noise. Otherwise, the circuit met the desired output result.

PRECAUTIONS:i) Here electrolytic capacitors are used. Their values are not accurate, errors of at least 20% is common.


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ii)

Electrolytic capacitors leak charge with substantially increase the time period. For example, a circuit which should be maximum time period of 2665(4.5 min), can be extended to even 10 minutes while using these electrolytic capacitors.

CONCLUSION:This assignment shows how a 555 Timer IC is configured to function as a basic monostable multivibrator. As it has only one stable O/P, it is also known as ONESHOT. So, from calculation of other parameters required to complete the circuit, we can construct the circuit on bread broad, then finally on Vero broad.

ASSIGNMENT NO:-6 ASSIGNMENT NAME:-To design Full Subtractor using Multiplexer. Theory:Full subtractor: A full subtractor is a combinational circuit that performs subtraction involving three bits namely minuend bit, subtrahend bit and the borrow from the previous stage. Multiplexer: The term multiplex means many into one. Multiplexing is the process of transmitting a large number of information over a single line. A digital Multiplexer (MUX) is a combinational circuit that selects one digital information from several sources and transmits the selected information on a single output line. A multiplexer is also called a data selector, since it selects one of many Inputs and steers the information to output. The multiplexer has several data input lines and a single output line. The selection of a particular input line is controlled by a set of selection lines. Electronic Circuit Design| Lab Report 31

The selection lines decide the no. of input lines of a particular multiplexer. If the no. of n input lines in equal to 2m , then m select lines are required to select one of the n input lines. Truth Table Of A Full Subtractor: INPUTS Minuend bit(X) 0 1 2 3 4 5 6 7 0 0 0 0 1 1 1 1 Subtrahen d bit(Y) 0 0 1 1 0 0 1 1 Borrow In(Bin) 0 1 0 1 0 1 0 1 OUTPUTS Difference(D ) 0 1 1 0 1 0 0 1 Borrow out(Bout) 0 1 1 1 0 0 0 1

Calculation:-

Difference(D)= XY Bin+XYBin+XYBin+XYBin 00 0 1 14 01 11 17 11 12 10

D=m (1,2,4,7)-------------------1 Borrow Out(Bout)= XY Bin+XYBin+XYBin+XYBin Electronic Circuit Design| Lab Report 32

00 0 1

01 11 13 17

11 12

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Bout=m (1,2,3,7)-------------------2 CIRCUIT DIAGRAM:-

Conclusion:By these experiments, we have learnt how a full subtractor can be designed using two multiplexers. Advantages of this circuit are:Electronic Circuit Design| Lab Report 33

1. Here, no additional gates are required. & 2. It is faster than decoder.


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electronics circuit design lab

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