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Computer Fundamentals and Programming > Digital vs Analogue, Logic Devices, and Boolean Logic and Logic Gates > Flashcards

Digital vs Analogue, Logic Devices, and Boolean Logic and Logic Gates Flashcards

1
Q

What is the difference between analogue and digital signals?

A
  • Analogue signals has a continuously varying voltage

- Digital signals represent things as distinct voltage values (HIGH and LOW) (1 or 0)

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2
Q

What are the advantages of digital systems?

A
  • Known level of accuracy
  • Reliable (immune from interference, temperature/humidity and aging)
  • Can introduce intelligence
  • Can change the design easily
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3
Q

What are the disadvantages of digital systems?

A
  • Circuits are more complex (more wires0

- Increased cost of manufacture

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4
Q

What are the three basic logical operations?

A

OR, AND & NOT

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5
Q

What is a relay?

A
  • Electromagnetic device

- Allows current through a coil to close one or more independent set of switch contacts

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6
Q

What are the 2 states of a relay?

A

NO (normally open)

NC (normally closed)

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7
Q

What are the disadvantages of a relay?

A

Bulky, slow, unreliable and power hungry

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8
Q

What are the benefits of transistors?

A

Fast, very small, very reliable

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9
Q

What are transistors?

A
  • 3 terminal devices
  • an input voltage is applied to the control terminal which causes a conducting path between the other 2 terminals to be opened or closed
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10
Q

What is a CMOS FET?

A

Type of transistor where current flows between two electrodes (the source and the drain) via a channel. Above the channel, there is a gate (another electrode)
Acts as a switch

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11
Q

What is the difference between a N channel FET or a P channel FET?

A
  • N-channel FET uses the flow of electrons (output is HIGH when input is HIGH)
  • P-channel FETs uses holes (OUTPUT is HIGH when INPUT is LOW)
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12
Q

What are the values of Boolean logic?

A
  • 1 or TRUE (meaning HIGH or ON)

- 0 or FALSE (meaning LOW or OFF)

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13
Q

What are logic gates?

A

Logic gates are electronic circuits constructed from transistors with 1 or more input wire and 1 output wire

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14
Q

How does an OR gate function?

A
  • OUTPUT is HIGH if either or both INPUTs are HIGH

- OUT = A + B

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15
Q

How does an AND gate function?

A
  • OUTPUT is HIGH if both INPUTs are HIGH

- OUT = A.B

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16
Q

How does a NOT gate function?

A
  • OUTPUT is HIGH if INPUT is LOW

- OUT = A\

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17
Q

How does XOR gate function?

A
  • OUTPUT is HIGH if either INPUTs are HIGH but not both

- OUT = A+0B

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18
Q

How does NAND, NOR and XNOR function?

A
  • AND, OR and XOR gate respectively without inversions
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19
Q

Which gates can be used to implement all other operations?

A

NAND and NOR

20
Q

How do you make a NOT get from a NAND gate?

A

Split the input of the NAND gate into 2

21
Q

How do you make an OR from a NAND?

A

Connect 2 NOT gates (made from NANDs) to a NAND gate

- Represented in De Morgan’s Theorem

22
Q

What is De Morgan’s theorem?

A

A\ . B\ = (A+B)\

23
Q

How many inputs can OR and AND gates have?

A

Any number of inputs

24
Q

How many inputs can XOR and XNOR gates have?

A

2 inputs

25
Q

How many inputs can NOT gates have?

A

1 input

26
Q

What is the commutative law?

A
  • Order of the variables makes no difference

- AB = BA

27
Q

What is the associative law?

A
  • Grouping of variables makes no difference
  • A + (B + C) = ( A + B) + C = A + B + C
  • A(BC) = (AB)C = ABC
28
Q

What is the distributive law?

A
  • The operator outside the bracket operates on all variables inside the bracket
  • A(B + C) = AB + AC
  • A + (BC) = (A+B)(A+C)
29
Q

Solve A + 0

A

A

30
Q

Solve A + 1

A

1

31
Q

Solve A.0

A

0

32
Q

Solve A.1

A

A

33
Q

Solve A + A

A

A

34
Q

Solve A + A\

A

A

35
Q

Solve A.A

A

A

36
Q

Solve A.A\

A

0

37
Q

Solve A\

A

A

38
Q

Solve A + AB

A

A

39
Q

Solve A = A\B

A

A+B

40
Q

What is the SOP form?

A
  • Sum of Products form
  • When two or more product terms are summed by Boolean addition
  • eg. ABC + CDE + B\CD\
  • Can be directly translated into gates but may not be the most efficient design
41
Q

What is canonical form?

A
  • Standard SOP Form
  • All the variables in the domain appear in each product term in the expression
  • eg. f(A,B,C,D) = ABC\D + AB\CD + AB\CD\
  • each product term s known as a minterm
  • not efficient but useful in analysis and design
42
Q

How do you convert SOP to Canonical SOP?

A
  • Multiply by (X + X) where X is the missing variable
43
Q

What is an SOP equal to if any of the product terms is equal to 1?

A

1

44
Q

What does f = SIGMA(3,6,7) mean?

A

The sum of the row numbers having TRUE minterms

45
Q

Why would you want to simplify things?

A
  • To minimize the cost of implementation (minimize the number of operations needed/number of gates)
  • Increases the speed of operation
46
Q

How can you minimize by Boolean Algebra?

A
  • Grouping (adsorption rules)
  • Multiplication by redundant variables (eg. (A+A)
  • De Morgan’s theorem

Computer Fundamentals and Programming (3 decks)

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