electronics & communication engineering

ELECTRONICS & COMMUNICATION ENGINEERING

5. TIME DIVISION MULTIPLEXING AND DEMULTIPLEXING

Aim:

1. To study the 4 channel analog multiplexing and de multiplexing

2. To study the effect of sampling frequency on output signal

characteristics.

3. To study the effect of input signal amplitude on the output signal

characteristics.

Apparatus required:

1. Time Division Multiplexing and de multiplexing trainer Kit.

2. Dual Trace oscilloscope

Theory:

In PAM, PPM the pulse is present for a short duration and for most of the time

between the two pulses no signal is present. This free space between the pulses

can be occupied by pulses from other channels. This is known as Time Division

Multiplexing. Thus, time division multiplexing makes maximum utilization of the

transmission channel. Each channel to be transmitted is passed through the low

pass filter. The outputs of the low pass filters are connected to the rotating

sampling switch (or) commutator. It takes the sample from each channel per

revolution and rotates at the rate of f s. Thus the sampling frequency becomes fs

the single signal composed due to multiplexing of input channels. These

channels signals are then passed through low pass reconstruction filters. If the

highest signal frequency present in all the channels is fm, then by sampling

theorem, the sampling frequency fs must be such that fs≥2fm. Therefore, the time

space between successive samples from any one input will be Ts=1/fs, and Ts

1/2fm.

DIGITAL COMMUNICATIONS LAB 1


Circuit Diagram:

Fig: 1 Time Division Multiplexing And Demultiplexing Circuit

Procedure:

There are 4 signal sources;

a) AF Signal generator

b) Triangular wave generator

c) Square wave generator and

d) Sine wave generator

1. Connect these four signals to four inputs of the Multiplexer. Adjust each signal

amplitude to be with in +/-2V (p-p) and frequency non-over lapping within a

frequency band of 300Hz.

2. Connect A, B output of 7476 to A1, B l inputs of Multiplexer.

3. Adjust the frequency of IC 8038 (Square wave, triangular wave generator) to

be around 32 KHz, so that each of the Four channels are sampled at 8 KHz.

4. Adjust the pulse width of 555 timers to be around 10µsecs.

5. Observe the 4 output pin 11 of 7476 on one channel 1and TDM output pin 13

of CD4052 on second channel of oscilloscope. Synchronize scope Internal-CH

1 mode. All the multiplexed channels are observed during the full period of the

clock (1/32 KHz).

6. Connect TDM output to comparator –ve input and saw tooth wave to +ve

Input. Observe the Comparator output. The PAM pulses are now converted in

to PWM pulses.



7. Connect the PWM pulses to TDM input of De multiplexer at pin 3 of second

CD4052. Observe the individual outputs Y0, Y1, Y2, and Y3 at pin 1, 5, 2 & 4

of CD4052 respectively. The PWM pulses corresponding to each channels

are now separated as 4 streams.

8. Take one output and connect it to Low Pass Filter and the Low Pass Filter

output to Amplifier. Observe the output of the amplifier in conjunction with the

corresponding input. Repeat this for all 4 inputs. This is the Demodulated

TDM output. Any slight variation in frequency, amplitude is reflected in the

corresponding output.

Observations:

S.No Type of Signal

Input Signal Multiplexed output

Amplitude

(Vp-p)

Time period

(ms)

Time

Slot(ms)

No. of

cycles

1 AF signal 2 3.4 1.5 7

2 Sine wave 2 3.4 3.6 2

3 Square wave 2 3.4 2.4 1

4 Triangular wave 2 3.4 2 1

(a)



(b) Fig: 2 Waveforms of (a) AF Signal and Triangular Wave (b) Square and Sine

Wave

Fig: 3 Multiplexed Output Waveform



(a)

(b)

Fig: 4 Output Waveforms for (a & b) Demultiplexing Circuit

Inference:

Time division multiplexing and de multiplexing are observed.



Questions:

1. What is TDM?

A. The TDM process produces a bandwidth expansion factor ‘N’

independent message sources into a time slot equal to sampling

interval.

2. Applications of TDM?

A. Telephony.

3. What is the effect of amplitude and frequency of input signals on

output?

A. If the amplitude and frequency of the output signal is varied in

accordance with the input signal.



6. PULSE CODE MODULATION AND DE MODULATION

Aim:

To obtain the pulse code modulation and de modulation signals.

Apparatus required:

1. PCM trainer kit

2. Dual Trace Oscilloscope.

Theory:

Pulse Code Modulation is known as digital pulse modulation technique. In fact,

the pulse code modulation technique that the message signal is subjected to a

great number of operations. It consists of 3 main parts i.e., transmitter,

transmission path and receiver. The essential operations in the transmitter of a

PCM system are sampling, quantizing and encoding. Sampling is the operation in

which an analog signal is sampled according to the sampling theorem resulting in

a discrete time signal. The quantizing and encoding operations are usually

performed in the same circuit which is known as an ADC. Also, the essential

operations in the receiver are regeneration of impaired signals, decoding and

demodulation of the train of quantized samples. These operations are usually

performed in the same circuit which is known as digital to analog converter.

Further at intermediate points along the transmission route from the transmitter to

the receiver, regenerative repeaters are used to reconstruct the transmitted

sequence of coded pulses in order to combat the accumulated effects of signal

distortion and noise. The quantization refers to the use of a finite set of amplitude

levels and the selection of a level nearest to a particular sample value of the

message signal as the representation the system at transmission in which

sampled and quantized values of an analog signal are transmitted via a

sequence of code words is called Pulse Code Modulation. Two most commonly

used versions are the differential pulse code modulation and delta modulation.

The PCM communication system is shown in Fig1. In the circuit is often called an

analog to digital converter. The functional block that performs the task of

accepting binary digits and generating appropriate sequences of levels is called a

digital to analog converter. The bandwidth of PCM will be much greater than that



of the message. PCM is used to convert analog signals to binary form. Low pass

filter may be used to reduce the quantization noise and it yields the original

message signal.

Circuit Diagram:

Fig: 1 Pulse Code Modulation and Demodulation Circuit

Procedure:

1. Make the connections as per the diagram as shown in the Fig.1.and

switch on the power supply of the trainer kit.

2. Clock generator generates a 20 KHz clock .This can be given as

input to the timing and control circuit and observe the sampling

frequency fs= 2 KHz approximately at the output of timing and control

circuit.

3. Apply the signal generator output of 6V(p-p) approximately to the A to

D converter input and note down the binary word from LED’s i.e. LED

“ON” represents ‘1’ & “OFF” represents ‘0’

4. Feed the PCM waveform to the demodulator circuit and observe the

waveform at the output of D/A which is quantized level.



Observations:

Amplitude: 7v (p-p)

Frequency: 100Hz

Amplitude: 6v (p-p)

Frequency: 2 KHz

(b)

Amplitude: 3.68v (p-

p)



(c)

Fig: 2 Waveforms of (a) Modulating Signal (b) Sampling Signal (c) PCM output

Amplitude: 6.4v (p-p)

Time period: 8ms

Frequency: 122.2Hz

Fig: 3 Output Waveform for Demodulation Circuit

Apply the DC control voltage

DC voltage(v)

Bit sequence

MSB LSB

-41100 0111

-31010 1101

-21001 0111

40001 0111

50011 1111

Inference:

Recovery of the transmitter information does not depend on the height, width (or)

energy content of the individual pulses but only on their presence or absence.

Thus noise immunity of a PCM signal is much more than any analog pulse

modulation signal.



Questions:

1. What is the need of parallel to serial converter?

A. To transmit all the bits in one channel.

2. What is the use of companding?

A. Companding is used to overcome quantizing noise in PCM.

3. What are the applications of PCM?

A. Because of high immune to noise it can be used for storage systems in

CD recording.



7. DIFFERENTIAL PULSE CODE MODULATION AND DEMODULATION

Aim:

To study the differential PCM & demodulation by sending variable

frequency sine wave & variable DC signal input.

Apparatus required:

1. AF oscillator

2. DPCM modulator

3. DPCM demodulator

4. Connecting wires

5. CRO - 30MHz

6. Variable DC Source – 1

Theory:

In this DPCM instead of transmitting a base band signal m(t) we send the

difference signal of Kth sample and (k-1) th sample value. The advantage here is

fewer levels are required to quantize the difference than the required to quantize

m(t) and correspondingly, fewer bits will be needed to encode the levels. If we

know the post behaviour of a signal up to a certain time, it is possible to make

some interference about its future values this is called prediction. The filter

designed to perform the prediction is called a predictor. The difference between

the interest and the predictor o/p is called the prediction error.

Circuit Diagram:



Fig:1 Differential Pulse Code Modulation Circuit

Fig: 2 Differential Pulse Code Demodulation Circuit

Procedure:

1. Switch on the experimental kit.

2. Apply the variable DC signal of amplitude 6v(p-p) with frequency of 80Hz

to the input terminals of DPCM modulator.

3. Observe the sampling signal of amplitude 5v (p-p) with frequency 20KHz

on channel 1 of a CRO.

4. Observe the output of DPCM on the second channel.

5. By adjusting the DC voltage potentiometer, observe the DPCM output.

6. During the demodulation connect DPCM output to the input of

demodulator and observe the output of DPCM demodulator.

Observations:



Amplitude: 5v(p-p)

Frequency:20KHz

Amplitude: 6v(p-p)

Frequency:80Hz


(c)

Fig: 3 Waveforms of (a) Sampling Signal (b) Modulating Signal (c) DPCM Output




Step width: 1.4ms

(a)

-

(b)

Fig. 4 Output of (a) D/A Converter (b) Demodulated

Inference:

The DPCM wave forms were generated and they are demodulated for DC input

signals. By using DPCM the overall bit rate is decreases and number of bits

required to transmit one sample is also reduced

Questions:

1. What is the effect sampling signal?

A. Sampling time interval should be greater than the A to D conversion time.

2. Write the advantage of DPCM compared with PCM?



A. It reduce the transmission bandwidth and for a constant signal to quantizing

noise ratio and a sampling rate of 8khz, the DPCM provides a saving of about

8-16 bit per second over standard PCM.

3. What is the one bit version of DPCM?

A. Delta Modulation is the one bit version of DPCM.

8. DELTA MODULATION

Aim:

To obtain the delta modulation and demodulation signals.

Apparatus required:

1. Delta Modulation & Demodulation Kit

2. Cathode Ray Oscilloscope 0-30MHz

Theory:

Delta modulation uses a single bit PCM code to achieve digital transmission of

analog signals with conventional PCM each code is binary representation of both

the sign and magnitude of a particular sample. With delta modulation, rather than

transmit a coded representation of the sample, only a single bit is transmitted,

which indicates whether that sample is larger or smaller than the previous

sample. The algorithm for a delta modulation system is quite simple. If the

current sample is smaller than the previous sample, a logic 0 is transmitted. If the

current sample is larger than the previous sample, a logic 1 is transmitted. The

input analog is sampled and converted to a PAM signal, which is compared to

the output of the DAC. The output of the DAC is a voltage equal to the

regenerated magnitude of the previous sample, which was stored in the up/down

counter as a binary number, The up/down counter is incremented or

decremented depending on whether the previous sample is larger or smaller than

the current sample. The up/down counter is clocked at a rate equal to the sample

rate. Therefore, the up/down counter is updated after each comparison.

Block Diagram:



Fig: 1 Delta Modulation Circuit

Fig: 2 Delta Demodulation Circuit

Procedure:

1. Switch on the experimental board.

2. Connect the clock signal of frequency of 10KHz,with amplitude of 5v(p-p)

to the delta modulator circuit.

3. Connect the modulating signal of amplitude 5v(p-p) and frequency of of

0.2KHz modulating input of the delta modulator

And observe the same on channel 1 of a Dual Trace oscilloscope.

4. Observe the Delta Modulator output on channel 2.

5. Connect this Delta modulator output to the Demodulator

6. Also connect the clock signal to the demodulator.

7. Observe the Demodulator output with and without RC filter on CRO.



Observations:

(a)

(b)



(c)

Fig: 3 Waveforms (a) Clock input (b) Delta modulation output & message signal

(c) D/A converter output



Fig: 4 Output Waveform for demodulating signal

Inference:

Delta Modulation signal is generated and demodulated.

Questions:

1. What is the slope overload effect?

A. In general the step size we choose to quantize is fixed. So under

maximum slope of the signal this step size becomes small to follow the

steep of the input waveform. This condition is called slope - overload and

the resulting quantizing error is called slope – overload noise.

2. What is granular noise?

A. Granular noise corresponds to the error due to quantization in the ‘1’ bit

coding process.

3. Write the advantage of DM over PCM?

A. Dm transmits only one bit for one sample, thus the signaling rate and

channel bandwidth is very small, where as in PCM 4,8,or 6 bits are used per

sample.

4. What is the effect of the Low Pass Filter cut off frequency on output of

demodulator?

A. If the modulating signal frequency is higher than the low pass filter cut off

frequency the signal will be attenuated.

9. FREQUENCY SHIFT KEYING

Aim:

To generate the waveforms of frequency shift keying

Apparatus required:

Name of the apparatus Specifications/Range Quantity

Resistors 33kΩ 2

Capacitors 0.01µF, 100pF Each one

Function Generator 0-1MHz 1

RPS 0-30V, 1A 1

CRO 0-30MHz 1



IC 8038Supply voltage - ±18V or

36VPower dissipation – 750mW

1

CRO Probes ---- 1

Theory:

FSK signaling schemes find a wide range of applications in low-speed digital

data transmission system. FSK schemes are not as efficient as PSK interms of

power and bandwidth utilization. In binary FSK signaling the waveforms are used

to convey binary digits 0 and 1 respectively. The binary FSK waveform is a

continuous, phase constant envelope FM waveform. The FSK signal bandwidth

in this case is of order of 2MHz, which is same as the order of the bandwidth of

PSK signal.

Circuit Diagram:



Fig: 1 Frequency Shift Keying

Procedure:

1. Connect the circuit as shown in fig.1

2. Apply the (binary) Data input of amplitude 20V (p-p) with frequency of 6 KHz

from function generator to pin no.7.

3. Give the power supply of 10v to the appropriate pins.

4. Observe the FSK output at pin no.2.

5. Now note down the mark and space frequencies for different carrier

frequencies.

6. Calculate the maximum frequency deviation and modulation index.

7. Repeat the steps (5) and (6) for different pulse durations of binary input.

Observations:



Amplitude: 5v (p-p)

Frequency: 50 KHz

Amplitude: 20v (p-p)

Frequency: 6 KHz

Positive width:

90.80µs

Negative width:

87.42µs


Time period: 48µs

Frequency: 20.83

KHz

Positive width:

12.45µs

Negative width:

35.55µs



(c)

Fig: 2 Waveforms of (a) Carrier wave (b) Data input (c) FSK Wave


Frequency: 5.6 KHz

Time Period: 178µs

Fig: 3 Output Waveform for Demodulated Signal

Inference:

The frequency of the sinusoidal carrier is switched depending upon the i/p

binary signal

Questions:

1. Write the advantage of FSK compared to ASK?

A. It has constant modulated signal envelope and equal conditional error

probability for both the digits.

2. What is the disadvantage of FSK compared with ASK & PSK?

A. The bandwidth of FSK signal is higher than that of ASK &PSK signal

3. What is the effect of R1, C2 values on the output?

A. If R1, C2 values are changed the time period of the carrier will change.



10. PHASE SHIFT KEYING

Aim:

To generate the waveforms of phase shift keying.

Apparatus required:

Name of the apparatus Specifications/Range Quantity

Diodes(IN4007) Max Voltage:45V 4

Transformers 7V-0-7V 2

Function Generator 0-1MHz 2

CRO 0-30MHz 1

CRO Probes ---- 1

Theory:

Circuit diagram of PSK as shown in Fig.1. The phase of carrier is shifted between

two values is called Phase Shift Keying. The amplitude of carrier remains

constant. Phase Shift Keying is also called Phase Reversal Keying. The

performance of PSK is more than ASK. PSK is a non linear modulation. PSK

needs a complicated. Synchronous circuit at the receiver. The bandwidth of PSK

is 2fm.

Circuit Diagram:



Fig: 1 Phase Shift Keying Circuit

Procedure:


2. Apply the carrier signal of amplitude7v (p-p) with frequency of 4 KHz to the

modulator input and observe the signal on the channel of the CRO.

3. Apply the modulating signal of amplitude 6V (p-p) and frequency of 0.5 KHz

to pin.11.

4. Observe the output of PSK modulator on the channel 2 of the CRO.

Observations:

(a)



Amplitude: 6v (p-

p)

Frequency: 1 KHz

Amplitude: 6v (p-p)

(c)

Fig: 2 Waveforms of (a) Carrier signal (b) Modulating signal (c) PSK output

Inference:

The PSK waveform was generated for different message signals .and the phase

of the carrier is switched depending upon the input binary signal

Questions:

1. Drawback of DPSK compared to BPSK?

A DPSK uses two successive bits for its reception .error in the first bit creates

error in the second bit. Therefore error propagation in DPSK is more .on the

other hand in BPSK single bit can go in error since detection of each bit is

independent

2. Write the advantage of BPSK over the BPSK?



A Bandwidth requirement of BPSK is double the bandwidth requirement of

BPSK

3. What is the effect of carrier amplitude on the output?

A. The amplitude of the output can be varied by changing the carrier amplitude.

4. What is the effect of modulating signal frequency on the output?

A. The phase difference interval can be varied by changing the frequency of the

modulating signal

11. DIFFERENTIAL PHASE SHIFT KEYING MODULATION

AND DEMODULATION

Aim:

To study the various steps involved in generating the differential phase

shift keyed signal and the binary signal from the received DPSK signal

Apparatus required:

1. DPSK trainer board

2. Cathode Ray Oscilloscope (0-30MHz)

Theory:

The differentially coherent PSK signaling scheme make use of a technique

designed to get around the need for a coherent reference signal at the receiver.

In the DPSK scheme, the phase reference for demodulation is derived from the

phase of the carrier during the preceding signaling interval, and the receiver

decodes the digital information based on the differential phase.

Circuit Diagram:



Fig: 1 Differential Phase Shift Keying Circuit

Procedure:


2. Check the carrier signal and the data generator signals initially.

3. Apply the carrier signal of amplitude 6v (p-p) with frequency of1KHz to the

carrier input, the data input of amplitude 5v (p-p) with frequency of 600Hz

to the data input and bit clock of amplitude 5v (p-p) with and frequency of

1 KHz to the DPSK modulator.

4. Observe the DPSK wave of amplitude 5.6v (p-p) and frequency of 1 KHz

with respect to the input data generated signal of dual trace oscilloscope.

5. Give the output of the DPSK modulator signal to the input of demodulator,

give the bit clock output to the bit clock input to the demodulator and also

give the carrier output to the carrier input of demodulator.

6. Observe the demodulator output with respect to data generator signal.

Observations:



(a)

(c)



Amplitude: 5.6v

Frequency: 1.16 KHz

Time period: 860µs

Fig: 2 Waveforms of (a) Carrier signal (b) Bit clock (c) Data input (d) Differential

data (e) DPSK wave

Fig: 3 Output Waveform for demodulated Wave



Inference:

The DPSK waveform was generated and demodulated for the binary

message signal.

Questions:

1. Write the advantage of DPSK?

A. DPSK does not need a synchronous carrier at the demodulator

2. What is the drawback of DPSK compared to PSK system?

A. DPSK uses two successive bits for its reception .error in the first bit creates

error in the second bit. Therefore error propagation in Dpsk is more .on the

other hand in BPSK single bit can go in error since detection of each bit is

independent.

3. What is the effect of carrier amplitude on the output of DPSK?

A. The amplitude of the DPSK is same as the amplitude of the carrier signal

if it is varied the amplitude of the DPSK will vary.

12. AMPLITUDE SHIFT KEYING

Aim:

To generate the waveforms of Amplitude Shift Keying.

Apparatus required:

Name of the Apparatus Specifications/Range Quantity

Resistors 1.2KΩ, 3

Transistor BC 107 2

CRO 30MHz 1



Function generator 0-1MHz 1

Regulated Power Supply 0-30V, 1A 1

CRO Probes --- 1

Theory:

The binary ASK system was one of the earliest form of digital modulation used in

wireless telegraphy. In an binary ASK system binary symbol 1 is represented by

transmitting a sinusoidal carrier wave of fixed amplitude Ac and fixed frequency fc

for the bit duration Tb where as binary symbol 0 is represented by switching of the

carrier for Tb seconds. This signal can be generated simply by turning the carrier

of a sinusoidal oscillator ON and OFF for the prescribed periods indicated by the

modulating pulse train. For this reason the scheme is also known as on-off shift

testing. Let the sinusoidal carrier can be represented by Ec (t) =Ac cos (2Πfct)

then the binary ASK signal can be represented by a wave s(t) given by S(t) =

Accos(2Πfct), symbol 1 ASK signal can be generated by applying the incoming

binary data and the sinusoidal carrier to the two inputs of a product modulator.

The resulting output is the ASK wave. The ASK signal which is basically product

of the binary sequence and carrier signal has a same as that of base band signal

but shifted in the frequency domain by ±fc. The band width of ASK signal is

infinite but practically it is 3/Tb.

Circuit Diagram:



Fig: 1 Amplitude Shift Keying Circuit

Procedure:

1. Connect the circuit as per the circuit diagram.

2. Switch on the supply.

3. Apply the sinusoidal carrier signal from the function generator to the collector

terminal of the transistor with 10v (p-p) amplitude and10KHz frequency.

4. Apply the Binary signal from the pulse generator to the Base terminal of the

transistor with 5v (p-p) amplitude and 2 KHz frequency.

5. Observe the output of ON/OFF keying from ASK modulator circuit using CRO.

6. Now vary the Amplitude and frequency of the binary signal and observe the

output changes of ASK modulated Wave & compare it with the modulating

data signal applied to the modulator input.

Observations:



(a)

Amplitude: 4v (p-p)

Frequency: 2 KHz

Amplitude: 4v (p-p)

Frequency:2KHz

(b)

Fig: 2 Waveforms of (a) Carrier signal (b) Data signal & ASK wave

Inference:

The ASK waveform was generated for different values of message signal. And

amplitude of the carrier is switched depending on the input binary signal

Questions:

1. Why we are not preferred ASK over PSK and FSK?



A Because of constant amplitude of FSK & PSK the effect of non linearties,

noise interference is minimum on signal detection However these effects are

more pronounced on Ask

2. What is another name of ASK modulation scheme?

A. ON –OFF Keying

3. What is the Effect of carrier amplitude, frequency, V cc on the output?

A. The amplitude of the output varies depending upon the V cc and the amplitude

of the carrier.

APPENDIX

Name of the Important Specifications Pin Diagram



component

74LS00

Supply Voltage Min – 4.75V

Supply Voltage Max – 5.25V

Operating temperature Range – 0oC to

+70oC

Output Current High max - -0.4mA

Output Current Low Max- 80mA

74LS08




+70oC

Output Current High Max - -0.4mA


74LS74




+70oC

Power supply current - 8.0mA

74138




+70oC

Output Current High Max - -0.4mA


74194




+70oC


Output Current Low max - 80mA



74LS374



High level input voltage min – 2V

Low level input voltage max– 0.8V

High level output current max – -2.4mA

Low level output current max- 24mA


+70oC

74151




+70oC



74LS163




+70oC





74LS164




+70oC



74165



Free air operating temperature- 0oC to

+70oC

Supply Current max – 36mA

Clock frequency – 25MHz

Pulse width (Clock) – 25ns

74168




+70oC

Power supply current – 34mA

74193 Supply Voltage Min – 4.75V



+70oC



Clock frequency – 25MHz

Supply Current max – 34mA

74LS86




+70oC



74LS90




+70oC



LM311

Input voltage Range - -14.5V to 13V

Voltage gain – 40V/mV

Saturation voltage – 1.5V

Positive Supply Current – 7.5mA

Negative Supply Current – 5mA

LM324

Wide power supply rating – 3V to 32V


+70oC

Storage temperature - (-65oC to +150oC)



DAC0800

Supply Voltage – 5V

Operating temperature Range – (-55oC to

+125oC)

Power Dissipation -500mW

Input current – 5mA

Storage temperature - (-65oC to +150oC)

ADC0800

Supply voltage – ±5V

Clock range – 50 to 800KHz

Operating temperature Range – (-55oC to

+125oC)

Power supply current – 20mA

CD4051

Supply voltage - +5V to 18V

Operating temperature Range – (-40 oC to

+80oC)

Storage temperature - (-65 oC to +150oC)

Power dissipation – 700mW

CD4052

Supply voltage - +5V to 18V

Operating temperature Range – (-40 oC to

+80oC)

Storage temperature - (-65 oC to +150oC)


8038 Simultaneous outputs – sine wave

Square wave and Triangle

Low distortion – 1%

High linearity – 01%

Easy to use – 50% reduction in external

components

Wide frequency range of operation 0.001

Hz to 1.0Mhz

Variable duty cycle – 2% to 98%



Supply voltage - ±18V or 36V total


Input voltage (any pin) Not to exceed

supply voltages

Input current (pins 4 and 5 ) – 25mA

Operating temperature range: 55oC to

+125oC

μA741

Supply Voltage ±22V

Power Dissipation 500mW

Differential input voltage ±30V

Input voltage ±15V

Operating Temperature -55o to +125oC

Storage Temperature range -55o to

+150oC

TL084

Supply Voltage ±18V

Power Dissipation 680mW

Input voltage ±15V

Operating Temperature -0o to +70oC

Storage Temperature range -65o to

+150oC

IC 555

Operating tem :SE 555 -55oC to 125oC

NE 555 0o to 70oC

Supply voltage :+5V to +18V

Timing :µSec to Hours

Sink current :200mA

Temperature stability :50 PPM/oC change

in temp or 0-005% /oC.



REFERENCES:

Digital Communications - by John Proakis, TMH

Communication Systems - by Simon Hay kin, John Wiley

Communication Systems –by Sanjay Sharma

Digital Communication Fundamentals & Applications –by

Bernard Sklar

Principles of Digital Communications – by P.Chakrabarthi


electronics & communication engineering

Documents

b output

output signal characteristics

multiplexed output time

discrete time signal

corresponding output

time division multiplexing

signal sources

message signal