2 Marks ADIC

8/6/2019 2 Marks ADIC

1/21

Unit 1

1.What is meant by FAN-IN & FAN-OUT?

The fan-in of a digital logic gate refers to the number of inputs. A logic designer has to select

the fan-in to accommodate the number of inputs.e.g. a 2 input NOR gate has a fan-in of 2. Fan-

out is defined as the maximum number of inputs of the same IC family that the gate can drive

maintaining its output levels within the specified limit.

2.What is noise margin?

The noise margin allows the digital circuit to function properly if noise voltages are within the

limits of Vnh and Vnl for a particular logic family. The noise immunity of a logic circuit refers

to the circuits ability to tolerate the noise without causing spurious changes in the output voltage.

3.What is the propagation delay?

Propagation delay is otherwise called as Gate delay. It is basically the time interval between the

application of an input pulse and the occurrence of the resulting output pulse, at the time same it

limits the speed at which they can operate.

4.What is power dissipation?

The amount of power than an IC can dissipates when an certain amount of electrical power is

applied for the operation. This power is supplied by one or more power supply voltages

connected the power pin(s) on the chip.

5.Define TTL.It is abbreviated as Transistor transistor logic, TTL is named for its dependence on transistors

alone to perform basic logic operations in saturation mode.

6.Define ECL.

Emitter Coupled Logic has been developed which prevents transistor saturation,thereby

increasing overall switching speed by using a radically different circuits structure, called Current

Mode Logic(CML).

7.Define RTL.

It is abbreviated as Register Transfer Logic which uses Registers as a primitive component in

the digit system instead of flip-flops. It is also described as the information flow and processing

tasks among the data stored in the registers in a concise and precise manner.


2/21

8.Define Tri-State TTL.

The tristate configuration is a third type of TTL output configuration. It utilizes the high-speed

operation of the totem-pole arrangement while permitting outputs to be wired-ANDed(connected

together).TTL allows three possible output stages: HIGH, LOW and low impedance.

9.What is totem-pole?

capacitance is rapidly charged or discharged through the low output impedance. Totem pole

transistor are used because they produce a LOW output impedance. This means that the output

voltage can change quickly from one state to the other because any stray output

10.Define Schottky TTL.

Schottky Diode is that it has very little capacitance and fast recovery time. So it can be switched

rapidly without storage time delays. Hence Schottky TTL uses smaller resistor values to help

improve switching times. This increase the average power dissipation to about 20mW.

11.Explain the TTL characteristics.

a.The operation of input circuit is similar to the DTL gate.

b.A typical transfer characteristics is as the input voltage is increased from zero, the output

remains constant till the input approaches one diode drop.

c.The TTL output characteristics is when the output stage of TTL serves as a source of current

to the load.

12. Explain the characteristics of ECL.(or)What are the advantages of ECL over TTL?

a. It is the fastest of logic families. The popular 10K and 100K ECL families offer propagation

delay as short as 1ns.

b. Transistor are not allowed to go into the completer saturation and thus eliminates the storage

delays.

c.Switching transients are less because power supply current is more stable than in TTL and

CMOS circuits.

13.What are the disadvantages of ECL.

a.As logic levels are kept close to each other, noise margin is reduced and it is difficult to

achieve good noise immunity.

b.Power consumption is more because transistors are not completely saturated.


3/21

14.Define HTL.

This is belongs to DTL IC family, but is specially designed for high threshold(HTL) or high

noise immunity(HNL), logic applications, so that it find use in industrial applications.

15.Define DTL.

The DTL is a low-cost saturated logic type digital IC family, which is almost an extension of

discrete logic circuits, It makes use of diodes and BJTs.

16.Define CMOS.

CMOS circuit contains both NMOS and PMOS devices to speed the switching of capacitive

loads. It consumes low power and can be operated at high voltages, resulting in improved noise

immunity.

17.Sketch the typical CMOS characteristics.

a.Operating speed: Slower than TTL series.(25ns to 100ns)

b.Every CMOS is vulnerable to the building up of electrical charge on its insulated gate.

18.What is the difference between Current Source and Current Sink.

The fan out capability of the gate is governed by its sourcing and sinking characteristics. But

the difference is the gate is a source for any succeeding circuits when its output is in 1 state and it

is a sink when its output is in 0 state. Each input terminal of the gate has to sink

2mA(maximum) when it has to be in 0 state as compared to less than 1 microamps when

sourcing for 1 state.

19.Explain the characteristics of Digital IC.

a.Logic flexibility.

b.Operating speed.

c.Availability of complex functions.

d.Power dissipation.

e.Supply voltage.

f.Noise immunity and Noise generation.

g.Fan-in and Fan-out.

20.What are the restrictions of totem-pole circuits in open collector TTL IC?

They are not suitable for the following areas,

a.Extending the gates to perform complex functions in an IC chip.


4/21

b.OR-tieing of output leads of different gates to perform additional functions.

c.Driving non-standard loads(e.g.electromechanical relays).

21.Classify the basic families of MOS.

a.PMOS- uses only P-channel enhancement MOSFETs.

b.NMOS-uses only N-channel enhancement MOSFETs.

c.CMOS(complementary MOS- uses both P- and N- channel devices.

22.What are the process involving in IC fabrication?

a.Wafer preparation.

b.Epitaxial growth.

c.Oxidation.

d.Photolithography.

e.Diffusion.

f.Ion implantation.

g.Isolation Technique.

h.Metallisation.

i.Assembly and Packaging.

23.What are the types of digital IC families.

DTL-Diode Transistor Logic

HTL-High threshold Logic.

TTL-Transistor transistor Logic.

RTL-Resistor Transistor Logic.

ECL-Emitter Coupled Logic.

24.What is I^2L ICs?

It is abbreviated as Integrated Injection Logic(IIL), sometimes also called as Merged Transistor

Logic(MTL), this process is quite attractive for LSI/VLSI realization. Its important features are:

a.The circuit is similar to RTL,except that there are no base resistors used.

b.The circuit uses BJTs, both pnp and npn. Therefore the operating speed is quite high.

25.What are the advantages and disadvantages of DTL?

ADVANTAGES:

a.Compatability with TTL ICs: this improves flexibility in system design.

b.Availability of many functions:AND,NAND,OR,NOR,Exclusive-OR,etc are available.


5/21

c.Ease of interfacing with discrete circuits.

d.Low power dissipation.

DISADVANTAGES:

a.Limited operating speed.

b.Low noise immunity,therefore not usefull in industrial applications.

c.High temperature sensitivity of threshold voltage.

d. Useful for SSI.

26. what are the application of DTL?

a.Counters,shift registers,etc.

b.Small computers.

c.Instrumentation.

27.What are the advantage and disadvantages of HTL?

ADVANTAGES:

a.Compatability with discrete circuits, linear ICs and electromechanical components.

b.Wired Output capability, when the output circuit load is passive.

DISADVANTAGES:

a.High power dissipation.

b.Low operating speed.

c.High cost.

28.List the application of HTL.

It is useful for all circuit applications in industrial environment employing motors, high voltage

switches,ON-OFF control circuits,etc.

29.What is the use BUS DRIVERS in TTL?

When devices are more, required current sourcing and sinking capabilities may exceed than

those provided by standard TTL. So the buffer ICs used for increasing the sinking ad sourcing

capability of bus are called bus drivers.

30.What is the difference between CMOS and TTL?

CMOS:

a.The input cannot be left open.

b.Power dissipation is very less

c.Fan out is more than TTL,typically 50.


6/21

d.More susceptible to noise.

TTL:

a.The input can be left open.

b.Power dissipation is more than CMOS,but it is constant depend on switching speed.

c.Fan out for TTL is 10.

d. Less susceptible to noise.

31.List the advantage of RTL.

a.The presentation of digital functions in register transfer function logic is very user friendly.

b.It describes the information flow which is very concise and precise in manner.

31.List the basic components to describe the RTL.

a.Registers and their functions.

b.Information.

c.Operations.

d.Control function.

32.How the impurity doping is controlled during the IC fabrication?

The impurity doping is controlled by varying the concentration of chlorides of impurity

elements in the epitaxial reaction chamber.


7/21

UNIT-II OPERATIONAL AMPLIFIER

1. Define CMRR?

The ability of a differential amplifier to reject a common mode signal is expressed by a

ratio called common mode rejection ratio denoted as CMRR.It is defined as the ratio of the differential voltage gain Ad to common mode voltage gain

Ac.

2. What are the applications of op-amp?Because of their low cost, small size, versatility, flexibility and dependability op-amps

are used in the fields of,

Process control and instrumentation. Computers and communication systems. Power and signal sources Measuring and display systems.3. Define input offset voltage?

The dc voltage, which makes the output voltage zero, when the terminal is grounded, is

called input offset voltage.The input offset voltage depends on the temperature.

4. Discuss the functions of buffer and level shifting stage in op-amp. ?The level shifting stage brings the dc level down to ground potential, when no signal is

applied at the input terminals. Then the signal is given to the last stage which is the output stage.The buffer is usually an emitter follower whose input impedance is very high. This

prevents loading of the high gain stage.

5. What are the basic requirements of input stage of an op-amp.?

The basic requirements of input stage of an op amp are:

1. High input impedance- to avoid loading on the sources.2. High voltage gain.3. Small input offset voltage.4. small input offset current5. High CMRR.6. Low input bias current.6. Define the differential gain of op amp.

The gain with which differential amplifier amplifies the difference between two input

signals is called differential gain of differential amplifier.Ad = V0 / Vd.

7. Define common mode gain of op-amp. ?The gain with which it amplifies the common mode signal to produce the output is called

common mode gain of the differential amplifier it is denoted as Ac.

8. Characteristics of ideal op- amp.

Infinite voltage gain Zero output impedance Infinite input impedance Zero offset voltage


8/21

Infinite bandwidth Infinite CMRR. Infinite slew rate.

9. Write any three characteristics of practical op-amp.?

Open loop gain: it is the voltage gain of the op-amp when no feedback is applied.Practically it is several thousands.

Input impedance: it is finite and typically greater than 1 M ohm. Output impedance: it is typically few hundred ohms. With the help of negative

feedback, it can be reduced to a very small value like 1 or 2 ohms.

Bandwidth: the bandwidth of practical op-amp in open loop configuration is verysmall. By application of negative feedback, it can be increased to a desired value.

Input offset voltage: the dc voltage, which makes the output voltage zero, whenthe other terminal is grounded is called input offset voltage.

10. Define slew rateThe slew rate is defined as the maximum rate of change of output voltage with time.

11. Define PSRR.

The power supply rejection ratio (PSRR) is defined as the ratio of the change in inputoffset voltage due to the change in supply voltage producing it, keeping other power supplyvoltage constant. It is also called power supply sensitivity (PSS)

12. Write the practical value of the following of IC 741.

s.no Parameter Practical value

1 Open loop voltage gain 2*10^5

2 Output impedance 75 ohms

3 Input impedance 2 m ohms4 Input offset current 200 nano A

5 Input offset voltage 2 milli volt

6 Bandwidth 1 meg hertz

7 CMRR 90 dB

8 Slew rate 0.5 V/ micro sec

9 Input bias current 80 nano A

10 Power supply rejection ratio (PSRR) 30 micro volt / V

13. Why op amp cannot be used in open loop configuration?

Due to high open loop gain, op amp either shows +V sat or V sat level. This indicatesthe inability of op amp to work as a linear small signal amplifier in the open loop mode. Hence,

the op amp is generally not used as amplifier in the open loop configuration.

14. What is the advantage of negative feedback in op amp circuit?

Reduced Open loop gain. Improves stability Reduces frequency distortion


9/21

It reduces the non linearity and noise in op amp Improves frequency response

15. What are the basic requirements in output stage of op amp?

Large output voltage and output current swing capability Low output impedance Shout circuit protection Low quiescent power dissipation.

16. Write the operating modes of op amp?1. Open loop configuration

2. Closed loop configuration

17. State the concept of virtual ground?This means the differential input voltage Vd between the non inverting and inverting

input terminals is essentially zero.

If the non inverting terminal is grounded by the concept of virtual short, the inverting

terminal is also at ground potential, though there is no physical connection between the invertingterminal and the ground. This is the principle of virtual ground.

18. Explain the principle of zero crossing detectors?The basic comparator can be used as the zero crossing detector i.e., it compares the

signal voltage applied at one input of an op amp with a known reference voltage at the other

input, and produces either a high or a low output voltage, depending on which input is higher.

19. What are the important features of instrumentation amplifier?

The important features of instrumentation amplifier are,

High gain accuracy High CMRR High gain stability with low temperature coefficient. Low dc offset Low output impedance.

20. What is instrumentation amplifier?The measurement of the physical quantities is generally carried out with the help of a

device called as transducer, but most of the transducer outputs are generally of very low levelsignals such a low level signals are not sufficient to drive the next stage of the system, hence the

special amplifier which is used for such a low level amplification with high CMRR, high input

impedance to avoid loading, low power consumption and some other features is called

instrumentation amplifier.

21. Define precision rectifier?

The major limitation of rectifier circuit using diodes is that they cannot rectify thevoltages below cut-in voltage of diodes. A circuit which used for the rectification of voltage

below the cut-in voltage and provides the ideal diode characteristics is called precision rectifier.


10/21

22. List out the practical application of the integrator and differentiator?

Integrator:

In the analog computers. In solving the differential equations. In analog to digital converters. Various signal wave shaping circuits. In ramp generators.

Differentiator:

In the wave shaping circuits to detect the high frequency components in the input signal. As a rate-of change detector in the FM demodulators.23. Why instrumentation amplifier should have high slew rate and input impedance?

The slew rate of the instrumentation amplifier must be as high as possible to provide

maximum undistorted output voltage swing.It should have high input impedance in order to avoid the loading of input sources.

24. Mention the advantages of instrumentation amplifier using op amp?The advantages of this circuit are,

The gain variation is easy and precise. Gain depends on external resistances and hence can be adjusted accurately and made

stable by selecting high quality resistances.

The input impedance depends on the input impedance of non inverting amplifiers which isextremely high.

The CMRR of the op amp A3 is very high and most of the common mode signal will berejected.

25. Write some applications of instrumentation amplifier?

The instrumentation amplifier along with the transducer bridge can be used in many practicalapplications some of them are temperature controller, temperature indicator, light intensitymeter, analog weight scale.

26. Define V I and I V converter?

V-I converter: It is the circuit in which the output load current is proportional to the inputvoltage. Depending upon the connection of load there are two types of V I converter namely

floating load type and grounded load type

I-V converter: It is the circuit in which the output voltage is proportional to input current.

27. What are other names of V-I converter and I-V converter?V-I converter is also known as Transresistance amplifier or voltage controlled current source.

I-V converter is also known as Transconductance amplifier or current controlled voltage source.

28. What are the application of V-I converter?The various application of V-I converter are

Low voltage dc voltmeter Low voltage ac voltmeter Diode tester and match finder Zener diode tester


11/21

29. What are the applications of I-V converter?The I-V converters were used in photodiode detector, photoFET detector.

30. What is comparator and write the type of comparator?A comparator is a circuit which compares a signal voltage applied at one input of an op

amp with a known reference voltage at the other input.

There are two types of comparator namely inverting comparator and non-inverting comparator.

31. Write the limitations of the op amp as comparator?

1. To have better comparator accuracy op amp must have CMRR, high gain, andnegligible input offset current and input offset voltage.

2. To have better response time op amp output must switch rapidly, between saturation

levels and also respond instantaneously to any change of condition at its input.3. To have output compatibility with digital devices op amp output must swing between

two logic levels suitable for certain logic family.

32. Application of the comparator?The various application of the comparator are, Zero crossing detector ,Level detector,

Window detector, Duty cycle controller, Pulse generator, Time marker generator, Phase detector.

33. Define log and antilog Amplifier?Log amplifier: The circuit in which the output is obtained as the function of logarithm of

the input voltage Vin is called log amplifier. The output obtained in this circuit is in natural

logarithm to obtain the logarithm to base 10 proper scaling is to done.Log10 X = 0.4343 ln (X).

Antilog amplifier: The log amplifier can be easily turned around to provide antilog or

exponential function called as antilog amplifier. When compared to the log amplifier theposition of diode and resistor are interchanged.

34. What are the applications of the analog multiplier?

There is no. of applications of analog multiplier such as Frequency doublers, frequencyshifting, and phase angle detection, real power computation, squaring of signals, dividing and

multiplying two signals.

35. What is window detector?

Window detector is used to mark the instant at which an unknown input is between two thresholdlevels. It can be indicated using LEDs.

36. Applications of Schmitt trigger circuit?

Schmitt triggers used for eliminating comparator chatter. It is used in Wave shaping circuit. It is used as sine to square wave generator.

In is used for on and off of controllers.


12/21

UNIT III- Analog IC application

1. Define voltage regulator?Its an electronic circuit that provides a stable DC voltage independent of the load current,

temperature and AC line voltage variations.2. What are the types of voltage regulators?1.series regulator

2.switching regulator

3. What is meant by linear regulator?In series regulators ,the output voltage is controlled by the continuous voltage drop

taking place across the series pass transistor. Since the transistor conducts the active or linear

region.this regulators are also called linear regulators.

4. Mention the parts of series regulators?1.reference voltage circuit

2.error amplifier

3.series pass transistor4.feedback network

5. Mention the examples of monolithic regulators?

78XX/79XX series and 723 general purpose regulators.

6. What voltage options are available in 78XX/79XX voltage regulators?

There are 7 options available, such as 5V,6V,8V,12V,15V,18V,24V.

7. What are the characteristics of three terminal of IC regulators?1.V0 : the regulated output voltage is fixed at the value as specified by the manufacturer.

2.the unregulated input voltage must be atleast 2V more than the regulated output

voltage.3.I0max : the load current may vary from zero to rated maximum output current.

4.thermal shutdown: the IC has the temperature sensor which turns OFF the IC when it

becomes too hot.

8. Define line/input regulation ?It is defined as the percentage change in the output voltage for a change in input voltage

and it is expressed in mV.

9. Define load regulation?The change in the output voltage for a change in load current and it is expressed in mV or

percentage of V0.

10. Define ripple rejection?The IC regulator not only keeps the output voltage constant but also reduces the amount

of ripple voltage. It is expressed in dB.

11. What is the need of adjustable regulator?In the laboratory one may need variable regulated voltage or voltage that is not available

as standard fixed voltage regulator.this can be achieved by using a fixed three terminal regulator.

12. Limitations of three terminal IC regulator?1.not short circuit protection.

2.output voltage is fixed


13/21

13. Limitations of IC 723?1.It has no in-built thermal protection

2.it has no short circuit current limits

14. Limitations of linear voltage regulator?1.the input step-down transformer is bulky and the most expensive component of linear

RPS mainly because of low line frequency.2.due to low line frequency ,large values of filter capacitors are required to decrease the

ripple.

3.efficiency is very low

15. What is the function of the pass transistor in switched mode regulators and series

regulators?

In series , the pass transistor is operated in linear region to provide a controlled voltage

drop across it with a steady DC current flow.In switched mode , the pass transistor is used as a controlled switch and operated at cut-

off or saturated state.

16. What is meant by DAC converter ?A DAC accepts an n-bit input word in binary and produce an analog signal proportional

to it.

17. What is meant by ADC converter?

Its a quantizing process whereby an analog signal is converted into equivalent binary

word.

18. What are the 2 techniques used in DAC converter?Binary weighted resistor type

R/2R ladder type.

19. What is meant by current driven DAC?In this , the shunt resistors are used to generate n binary weighted currents which are

added according to switch positions controlled by the digital input and then converted intovoltage to give analog voltage.

20. Write the output voltage eq. of binary weighted type ?

V0= -VR(b12-1+b22-2+b32-3++bn2-n)

21. What are the drawbacks of binary weighted type?1.Wide range of resistor values are required

2.the wide range of resistors has restrictions on both higher and lower ends.for smaller

values the loading effect may occur.3.the finite resistance of the switches disturbs the binary weighted relationship among

various currents.

22. Advantages of R/2R ladder type?1.easier to build accurately as only two precision metal film resistors are required.

2.number of bits can be expanded by adding more sections of same R/2R values.

3.in inverted R/2R ladder , node voltages remain constant with changing input binarywords.


14/21

23. Define dual slope ADC?Dual slope conversion is an indirect method for A/D conversion where an analog voltage

and a reference voltage are converted into time periods by an integrated and then measured by acounter.

24. Advantages and disadvantages of dual slope ADC?

Highly accurateLow cost

Immune to temperature caused to variations in R and C.

The disadvantage is that speed is low

25. What is successive approximation converter?This technique uses a very efficient code search strategy to complete n bit conversion in

just n clock periods.

26. What is meant by integrating type ADC and mention its types?It performs conversion in an indirect manner by first changing the analog input signal to

a linear function of time or frequency and then to digital code. The types are

1.charge balancing ADC

2.dual slope ADC27. Define voltage-to-frequency converter?It produces a pulse train whose frequency is linearly proportional to an analog input

voltage.

28. Typical specifications of VFC?

Wide dynamic rangeAbility to operate to relatively high frequency

Low linearity error

High scale factor accuracy

29. What is meant by VFC factor ?It is defined as the modulation voltage required to produce the frequency shift for a VCO.

30. Define filter?A frequency selective electric circuit that passes electric signals of specified band of

frequencies and attenuates the frequency signals outside the band is called electric filter.

31. What are the types of passive filter ?

Low pass filterHigh pass filter

Band pass filter

Band reject filter

32. Define low pass and high pass filter?

Low pass filter allows low frequency signals and attenuates high frequency signals.High pass filter allows high frequency signals and attenuates low frequency signals.

33. When does the flattest pass band occurs in low pass filters?

It occurs for damping coefficient of 1.414.

34. What is the damping coefficient for bessels filter?It is heavily damped and has a damping coefficient of 1.73.


15/21

35. Define band pass and band reject filter?A BPF is a frequency selector which allows one particular band of frequencies to pass.

A BRF is a frequency selector which attenuates one particular band of frequencies topass.

36. What is meant by state variable filter?It uses two OP-AMP integrators and one OP-AMP adder to provide simultaneous second

order low pass, band pass and high pass filter responses.

UNIT IV-PLL &555 TIMER

1. What is the voltage controlled oscillator?

A voltage controlled oscillator is an oscillator circuit in which the frequency of oscillations

can be controlled by an externally applied voltage. The VCO provides the linear relationshipbetween the applied voltage and oscillation frequency.

2. What is the other name of VCO and what is it used for?

The other name of VCO is voltage to frequency converter.

VCO is used to produce square and triangular waveforms whose frequency is controlledby control voltage.

3. Draw the pin diagram of IC 566(VCO).

4. Draw the waveform for VCO obtained at output.

5. Draw the block diagram of VCO.

6. What is the output frequency of VCO and how can it be changed?

The output frequency of VCO isf o=2(Vcc-Vc)/CtRtVcc

It can be changed either by

1. Timing resistor (Rt)2. Timing capacitor(Ct)3. Voltage Vc at the modulating input terminal pin 5.

7. What is voltage to frequency conversion factor?The voltage to frequency conversion factor Kv is defined as

Kv= f o/ Vc

Vc is the modulation voltage required to produce the frequency shift f

for a VCO.

8. What are the applications of VCO?

The various application of VCO are:

1.FM modulation2.Signal generation(Triangular or Square wave)

3.Function generation.

4.In frequency multipliers.

9.What is a phase locked loop?A phase locked loop is basically a closed loop system designed to lock the output

frequency and phase to the frequency and phase of an input signal.

10. What is the phase detector and what are the two types of phase detector?A circuit that provides a dc output voltage which is related to the phase difference

between an oscillator signal and a reference signal to keep it in synchronism with reference

signal. The two stages are digital and analog.


16/21

11.When is the loop considered locked?

Loop is considered to be locked when input and output frequency are equal.For perfect lock the VCO output should be 90 degree out of phase with respect to the

input signal because at that time error voltage is zero.

12. What are the 3 stages of PLL?The three stages of PLL are free running, capture and locked or tracking.

13. Define lock in range.

The range of frequencies over which the PLL can maintain lock with the incoming signal

is called the lock in range or tracking range .The lock range is usually expressed as a percentageof fo the VCO frequency.

14.Define capture range.

The range of frequencies over which the PLL can acquire lock with an input signal is calledthe capture range. This parameter is also expressed as percentage of fo.

15. Define pull in time .

The total time taken by the PLL to establish lock is called pull in time. This depends on the

initial phase and frequency difference between the two signal as well as on the overall loop gainand loop filter characteristics.

16. In digital phase detector when will the maximum dc output voltage occur?

The maximum dc output voltage occurs when the phase difference is 180 degree becauseat that time the output of the Ex-OR gate is high.

17. What are the applications of PLL?

Frequency MultiplierFrequency Synthesizer

Frequency Shift Keying Demodulator

FM DetectorAM Detection

Frequency Translation

18. How can frequency multiplication be achieved using PLL?Frequency multiplication can be obtained by using PLL in its harmonic locking mode. If

input is square wave then VCO can be directly locked to the n-th harmonic of the input signal

without connecting any frequency divider in between.

19.What is the use of low pass filter in PLL?The low pass filter may be passive or active type. The LPF controls the capture range and

lock range of PLL.

20.What is the major difference between digital and analog PLL s?The analog multiplier is basis of analog phase detector ,here the output is filtered sum or

difference of two input frequencies. Whereas EX-OR is the basis of digital phase detector and

the output is symmetrical square wave at twice the input frequency.

21. What are the modes of operation of a timer?Timer can be used in monostable or astable mode of operation.

22.. What is the main purpose of timer circuits?

IC timer circuits can produce very accurate and stable time delays , microseconds tohours.

23.Draw the functional diagram of 555 timer


17/21

24.Why is a capacitor connected between pin 5 and ground in 555timer?A capacitor (0.01 F) is connected between control voltage terminal and ground to by-

pass noise or ripple from the supply.

25. Draw the monostable multivibrator using 555 timer?

26. What are the application of 555 timer?Application of 555 timer are as waveform generator,missing pulse detector , frequency

divider ,pulse width modulator, burglar alarm, FSK generator , ramp generator , pulse position

modulator etc.

27.What is the use of missing pulse detector circuit?Missing pulse detector circuit is used to detect missing heartbeats. It can also be used for

speed control and measurement.

28.Define duty cycle?The duty cycle, D of a circuit is defined as the ratio of ON time to the total time period T=(tON

+tOFF).

29.What is the output frequency in astable mode?

The output frequency in astable mode is,f=1.45/(Ra+2Rb)C

30.What are the application of 555 timer in astable mode?

The applications of 555timer in astable mode are FSK generator, Pulse-Position Modulator andSchmitt trigger.

31. How is a Schmitt Trigger constructed using 555?

For Schmitt trigger, in 555 timer two internal comparators are tied together and externallybiased at Vcc/2 through R1 and R2.

32. How is square wave output obtained from Schmitt trigger using 555 timer?

The sine waves of the amplitude exceeding the reference levels causes the internal flip flop toalternatively set and reset, which provides a square wave output.

UNIT-V-SYSTEM DESIGN

1. Define sample and hold circuits?

The sample and hold circuit sample the value of input signal in response to a sampling

command and hold it at the output until arrival of the next command.

2. What is the need of sample and hold circuits?

To minimise the occurrence of the errors it necessary to hold the value of the analog input

voltage constant during the conversion process. The sample and hold circuits does this task.

3. What are the advantage of sample and hold circuits?

a. The primary use of the sample and hold circuit to hold the sampled analog input voltage

constant during the conversion time of A/D converter.

b. It also reduces the crosstalk in the multiplexer.


18/21

4. List the application of sample and hold circuit.

a. Digital interfacing

b. Analog to digital converter circuits.

c. Pulse modulation systems.

5. Define Frequency synthesizer.

The frequency synthesizer is a laboratory signal source which offers the same stability and

purity for its output waveform as that of a standard frequency.

6. Explain the basic need to construct the frequency synthesizer.

Phase Locked Loop(PLL) can be used as the basis for frequency synthesizer.i.e. frequency

synthesizer comes under the application of Phase Locked Loop.

7. What is the function of PLL in frequency synthesizer?

The PLL produce the precise series of frequency that are derived from a stable crystal

controlled oscillator.

8.What is the difference between frequency synthesizer and frequency multiplier?

Though both are comes under the application of PLL , frequency synthesizer is similar to

frequency multiplier circuit , but the difference is divided by M network is added at the input of

phase lock loop,

9.Explain Function Generator.

The function generator is a laboratory signal source. Basically, it comprises a triangular

waveform generator whose frequency can be controlled smoothly as well as in steps.

10.What is the advantage of Function Generator.

a.The use of suitable sine wave synthesis circuit along with the function generator makes it

possible to obtain sine waveform from the triangular waveform.

b. The generator can also produce a square wave train at the same frequency as the triangular

wave train.

11List the waveform produced by the function generator.

a.Sine waveform from the triangular wave(using sine wave synthesis)

b.square wave from triangular wave train.

c.Triangular wave(equal positive and negative slopes as well as maximum amplitude.


19/21

12.How several tuning range can be obtained for function generator?

Several tuning ranges can be provided by switching in integrating capacitors of different values

at C, e.g. in decade steps.

13.How frequency is limited in the function generator?

Leakage resistance associated with Capacitor(in feedback path) limits the lowest frequency of

operation of the circuit,whereas the high frequency limit is brought about by the slew rate of the

OP-AMP.

14.What is voltage dependent attenuator circuit?

The synthesis of a sine wave from the triangular waveform is usually carried out by employing

a voltage dependent attenuator circuit in function generator. A biased diode resistor network or

FET circuit is very useful for this purpose.

15.Briefly explain the Pseudo Random Binary Sequence(PRBS).

PRBS is one form of the noise which can be easily generated in the laboratory.But its

amplitude probability distribution is not typical of natural random noise.However,it can be useful

in many applications, where the actuating signal are of the ON-OFF type.

16.What is the use of the noise signal?

Noise is required nowadays as a test signal for a variety of measurements,e.g, for the evaluation

of multichannel PCM systems, studies on biomedical phenomena,vibrating testing,

aerodynamics,seismology.

17.How to generate the PRBS waveform?

A shift register with suitable feedback is useful to generate the PRBS waveform. The inputs to

the feedback network, which have to be linear and follow combinational logic, are the outputs at

selected stages of the shift register.

18.How the length of the PRBS waveform is designed?

The maximum length of the PRBS waveform is (2^n-1) bits, where n is the number of stages in

the shift register. It can be obtained by a proper choice of the tappings for the shift register.

19.What is the role of clock frequency in PRBS generator?

The frequency of the PRBS waveform is the same as the clock frequency of the shift register.


20/21

20.List some of the important features of the PRBS generated by the shift register.

a.The sequence has an odd number of bits in the pattern i.e.(2^n-1)

b.Because the waveform is periodic, complete information on the statistics of the signal is

obtained by averaging over a time interval (2^n-1)*clock period.

21.List some display system in electronics.

Display systems are required for several applications in electronics. Digital

instruments,computers,calculators,aircraft and automobile instruments as well as consumer

items,such as clocks and wrist watches, are some popular examples of display applications.

22.List some display technologies in Display system and design.

The display of numeric data is commonly done using different display technologies of which

LEDs(Light emitting Diode) and LCDs (Liquid Crystal display) are the most popular now.

23. What is the use of CRT in LED(light emitting diode and LCD(liquid crystal display)?

For alphanumeric display applications,CRTs(Cathode Ray Tube) are the most widely used with

LEDs and LCDs closely following it.

24. What is Bar-graph display?

Bar-graph displays are analog displays which are useful in electronics instruments as trend

indicators of voltage and currents. They use a closely packed array(e.g. linear, semicircular) of

display elements(LED being very common) which are independently driven.

25.What is the difference between LED and LCD in power requirement and display mode?

a.The LEDs being active displays uses pn junction diodes in compound semiconductors(such

as GaAs,GaP)., are highly compatible with ICs and require low d.c. power. In contrast, LCDs are

passive displays making use of electro-optic effects in certain organic chemicals, but their

driving power requirements being more far lower than LEDs.

b.Being miniature point sources of light,LEDs are directly usable in dot-matrix form. But the

LCDs are usable either as transmissive displays or as reflective displays, the latter being more

popular from the point of view of power saving.

26.What is the use of strobing technique in 7-Segment LED display?

In addition to reducing the number of code converters and drivers, the strobing technique

provided a considerable saving in d.c. power to achieve the same display intensity.


21/21

27.How to achieve flickering free display?

The strobing frequency (which is used to refresh rate of the characters) is maintained at a high

value(>16Hz, preferably around 100 Hz) so that display appears free from flicker.

28.Briefly explain the design of a 5-digit display using 7-segmented LED.

The design of a 5-digit display system using 7-segment LED characters at the output of a digital

instruments(such as frequency counter) . In this, a set of 5 decade counters accumulate the count

at the end of every sample of measurement and it is required to display the same on the LED

characters.

29.What are the features of 7-Segment LCD?

a.The LCDs require very little power for operation; typically 1microamps at 5v.

b.LCDs have large turn-ON and OFF times typically 10s of msec.

c.LCDs characters are available with single back electrode or split back electrode construction.

30.What is the use of the Segmented LCDs?

Segmented LCDs can be used as static displays or dynamic displays.

31.What is meant by Digital Voltmeter?

The digital voltmeter(DVM) is an extremely useful laboratory instrument. It is also a useful

building block of digital instrumentation systems. The utility of a DVM can be easily extended to

multiple functions,e.g.digital multimeter(DMM) by the addition of simple auxiliary hardware.

32.List some of the advantage of Digital Voltmeter.

a.Low cost per element.

b.It is bright,efficient(good contrast in bright ambient light).

c.Low power consumption and it is compatible with ICs.

2 Marks ADIC

Documents

Transcript of 2 Marks ADIC