The document contains questions and answers related to operational amplifiers (op-amps) and digital electronics topics. Some key points: - Op-amps were originally used in analog computers to model mathematical operations and have ideal characteristics like infinite gain and input/output impedances. They are now widely used in applications like amplifiers, filters, comparators. - Schmitt triggers are used in oscillators, function generators, and switching power supplies. They introduce hysteresis to convert analog signals to digital square waves. - Digital logic gates like AND, OR, NOT are used to build combinational and sequential circuits. Flip-flops, counters, registers are examples of sequential circuits while adders, decoders are combin

1. ADE VIVA QUESTIONS
1. Why is the operational amplifier called by its name?
Op-amp stands for operational amplifier. Originally, op-amps were so named because they were used to model
the basic mathematical operations of addition, subtraction, integration, differentiation, etc. in electronic analog
computers. In this sense a true operational amplifier is an ideal circuit element.
2. Explain the advantages of OP AMP over transistor amplifiers.
Advantages:
i) increased circuit stability.
ii) increased input impedance.
iii) decreased output impedance.
iv) increased frequency bandwidth at constant gain.
3. List the OP AMP ideal characteristics.
➔ Infinite open-loop gain G = Vout / Vin
➔ Infinite input impedance Rin, and so zero input current.
➔ Zero input offset voltage.
➔ Infinite output voltage range.
➔ Infinite bandwidth with zero phase shift and infinite slew rate.
➔ Zero output impedance Rout
➔ Zero noise.
➔ Infinite common-mode rejection ratio (CMRR)
The ideal op amp is an amplifier with infinite input impedance, infinite open-loop gain, zero output impedance,
infinite bandwidth, and zero noise. It has positive and negative inputs which allow circuits that use feedback to
achieve a wide range of functions.
4. Give the symbol of OP AMP.
5. Explain the various applications of OPAMP.
Op amps are widely used in amplifiers oscillators, filters, comparators, integrators and
differentiation,voltage regulator, current regulator. Non linear applications include precision rectified log
amplifiers. It is also used in analog to digital and digital to analog converter.
Operational amplifiers are linear devices that have all the properties required for nearly ideal DC
amplification and are therefore used extensively in signal conditioning, filtering or to perform mathematical
operations such as add, subtract, integration and differentiation.
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2. 6. Define UTP and LTP.
UTP(Upper Trip Point) is the point in the raising part of input waveform, at which the
output voltage changes state . LTP (Lower Trip Point) is the point in the falling part of the
input waveform, at which the output changes state.
7. Mention the applications of Schmitt trigger.
➔ They are used in closed-loop negative feedback configurations in relaxation oscillators.
➔ used in function generators
➔ switching power supplies SMPS.
8. What is a square wave generator/Regenerative comparator?
A square wave generator is a non-sinusoidal waveform oscillator that is capable of generating square waves. The
Schmitt trigger circuit is an implementation of square wave generators. Another name for the square wave
generator is an Astable or a free-running multivibrator.
9. Give the hysteresis curve of a Schmitt trigger.
10. What is a bipolar and unipolar device? Give examples
Bipolar Transistors are “Bipolar” devices because they operate with both types of charge carriers, Holes and
Electrons. Ex: BJT. A Unipolar Transistor is a “Unipolar” device that depends only on the conduction of
electrons (N-channel) or holes (P-channel). Ex: FET.
11. Define resolution
Resolution of a D/A converter is defined as the smallest change that can
occur in the analog output as a result of a change in the digital input.
12. Explain the need of D/A and A/D converters.
A/D Converters : Microprocessors can only perform complex processing on digitised signals. When signals are
in digital form they are less susceptible to the delirious effect of additive noise. ADC provides a link between
the analog world of transducers and the digital world of signal processing and data handling.
D/A Converters : It is an electronic device that converts a digital code to an analog signal such as voltage,
current, or electric charge. Signals can easily be stored and transmitted in digital form: a DAC is used for the
signal to be recognised by human senses or non-digital systems.
13. List the different types of D/A and A/D converters.
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3. Types of A/D Converters:
➔ Flash A/D Converters
➔ Delta-Sigma A/D Converters
➔ Successive Approximation A/D Converter
Types of D/A Converters:
➔ Weighted Resistor D/A Converters
➔ R-2R Ladder D/A Converters
14. What is a multivibrator?
An electronic device that produces a non-sinusoidal waveform as its output is known as a Multivibrator.
15. What is a bistable multivibrator?
A type of multivibrator whose output consists of 2 stable states is known as Bistable Multivibrator.
16. Give the applications of monostable and astable multivibrators.
Astable multivibrator
● The astable or free running multivibrator is used as a square wave frequency generator
● As a timing oscillator or clock of a computer system.
● It is also used for flashing lights, switching and power supply circuits.
Monostable multivibrator
● The monostable multivibrator is used as delay and timing circuits.
● It is also used for temporary memories.
● It is often used to trigger another pulse generator.
● It is used for regenerating old and worn out pulses.
17. Why astable multivibrator is called a free running multivibrator.
In electronic circuits, astable multivibrators are also known as Free-running Multivibrator as they do not
require any additional inputs or external assistance to oscillate.
18. Define duty cycle.
Duty cycle is the ratio of time a load or circuit is ON compared to the time the load or circuit is OFF.
19. List the applications of 555 timer.
● The IC 555 is used for Tone generation.
● It is used to make an alarm circuit.
● They are also used for frequency division applications.
● The IC 555 is used as a relaxation oscillator.
● They are also used in digital counter circuits.
● IC 555 is widely used for electronics projects.
20. Define a logic gate
Logic gates are the basic building blocks of any digital system.
21. What are basic gates
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4. There are several basic logic gates used in performing operations in digital systems. The common ones are:
AND, OR and NOT.
22. Why are NAND and NOR gates called universal gates?
Because we can implement any Boolean function, which is in sum of products form by using NAND gates
alone. Similarly, we can implement any Boolean function, which is in product of sums form by using NOR gates
alone.
23. State De Morgan's Theorem.
DeMorgan's Theorem states that inverting the output of any gate results in the same function as the opposite
type of gate (AND vs. OR) with two inverted variables A and B. It is used to solve Boolean Algebra expressions.
It performs gate operations like NAND gate and NOR gate.
24. List the applications of EX-OR and EX-NOR gates.
generation of parity generation and checking units
25. What is a half adder?
A combinational logic circuit that performs the addition of two data bits, A and B, is called a half adder.
26. What is a full adder?
A combinational circuit that adds two data bits, A and B, and a carry-in bit, Cin, is called a full adder.
27. Differentiate between combinational and sequential circuits. Give examples.
The combinational circuit is incapable of storing data, whereas sequential circuits are capable of storing a given
amount of data in memory spaces allocated for the purpose. Combinational circuits examples comprise adders,
subtractors, decoders, encoders, etc. Sequential circuits are mainly used in flip-flops, latches and registers.
28. Give the applications of combinational and sequential circuits.
Combinational circuits examples comprise adders, subtractors, decoders, encoders, etc. Sequential circuits are
mainly used in flip-flops, latches and registers.
29. Define flip flop.
A flip flop is a device very much like a latch in that it is a bistable multivibrator, having two states and a
feedback path that allows it to store a bit of information. It is edge triggered and only changes state when a
control signal goes from high to or low to high.
30. What is an excitation table?
Excitation table is the modified or simplest form of truth table of flip flops. It is very useful to design sequential
circuits. The inputs of the excitation table are the present states and next states of the flip flops. The outputs can
be determined depending on which flip flop is used.
31. What is race around condition?
A race condition is an undesirable situation that occurs when a device or system attempts to perform two or
more operations at the same time.
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5. 32. How do you eliminate race around conditions?
➔ Increasing the delay of the flip flop
➔ Use of edge-triggered flip flop
➔ Use of master slave JK flip flop
33. What is Minterm and Maxterm?
A minterm is a product term in boolean function in which every element present is either in normal or in
complemented form.
Maxterm: A maxterm is a sum term in a boolean function in which every element present is either in normal or
in complemented form.
34. Define multiplexer/data selector.
A multiplexer (or mux), also known as a data selector, is a device that selects between several analog or digital
input signals and forwards the selected input to a single output line.
35. What is a demultiplexer?
A Demultiplexer is a data distributor read as demux. It is a process of taking information from one input and
transmitting over one of many outputs.
36. Give the applications of mux and demux.
Communication systems, telephonic systems, in logic gates for combinational circuits, etc.
37. What is an encoder and decoder?
The combinational circuits that change the binary information into N output lines are known as Encoders. The
binary information is passed in the form of 2N input lines. The output lines define the N-bit code for the binary
information.
The combinational circuit that changes the binary information into 2N output lines is known as Decoders. The
binary information is passed in the form of N input lines. The output lines define the 2N-bit code for the binary
information.
38. What is a priority encoder?
The priority encoder is a combinational logic circuit that contains 2^n input lines and n output lines and
represents the highest priority input among all the input lines. When multiple input lines are active high at the
same time, then the input that has the highest priority is considered first to generate the output.
39. What are counters? Give their applications.
Counter is a sequential circuit. A digital circuit which is used for counting pulses is known as a counter.
40. Compare synchronous and asynchronous counters.
In a synchronous counter, all the flip-flops are triggered by the same clock signal whereas in an asynchronous
counter, flip-flops are triggered with different clock signals. Unlike an asynchronous counter, the state of the
output bits changes simultaneously in a synchronous counter, without any ripple.
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6. 41. What is a shift register?
A register adequate for changing its binary data in one or both directions is known as a shift register.
42. What does LS stand for in 74LSOO?
Low-power Schottky.
43. What is positive logic and negative logic?
Positive logic inputs and outputs are also called active high. Negative logic inputs and outputs are called active
low.
44. What are code converters?
A converter that changes coded information to a different code system.
45. What is gray code?
It is a non-weighted code which belongs to a class of codes called minimum change codes. In this code while
traversing from one step to another step only one bit in the code group changes.
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