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Chapter 20 Digital Circuits © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Objectives Explain the difference.

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Presentation on theme: "Chapter 20 Digital Circuits © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Objectives Explain the difference."— Presentation transcript:

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2 Chapter 20 Digital Circuits

3 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Objectives Explain the difference between analog and digital systems. Convert decimal numbers to their binary equivalents and binary numbers to their decimal equivalents. Name seven types of logic gates.

4 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Objectives Explain the operation of various types of logic gates. Use truth tables to determine the output of a logic gate. Discuss two types of logic families.

5 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Objectives Explain the digital encoders and decoders. Explain analog-to-digital and digital-to- analog devices. List three types of flip-flops and explain their truth tables.

6 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. ICs Include transistors, diodes, resistors, and capacitors Major advantage is size Linear circuits –Used as amplifiers and have variable outputs Digital circuits –Used as switches and work in the on or off state

7 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Digital Fundamentals Binary numbering systemBinary Voltage logic levels Bits, nibbles, and bytesBitsnibblesbytes

8 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Digital Advantages Inexpensive, compared to analog systems Easier information storage Speed is greater than in analog systems Compatibility with computers Less effect from temperature changes

9 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Digital Characteristics Capable of replacing analog systems Cannot be distinguished from analog systems in most cases Information is handled using switching circuits Combination of logic gate and flip-flop circuits

10 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Binary Numbering System Digital circuits act in on or off states Comparable to a single-pole single- throw (SPST) switch –Switch in on position represents a 1

11 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Basic Counting Rules Digits must be recorded one after the other for each counting unit When count exceeds total number of available digits, a second column begins Decimal systems first column ends at 9, and second column begins at 10Decimal system

12 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Binary System 2 is comparable to decimal systems 10 2 moves to second column, becomes a 0 or 1

13 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Decimal to Binary Conversion Table

14 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Binary Numbers Count binary numbers on your fingers Number the fingers on your left hand as shown Fingers pointing up are 1s, fingers folded down are 0s

15 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Large Binary Numbers and Addition

16 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Voltage Logic Levels in Digital Circuits Type of logic circuitry or family affects operating voltages needed in a circuit Valid logic high rangeValid logic high Valid logic low rangeValid logic low Invalid value range, or intermediate rangeInvalid value rangeintermediate range

17 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Bits, Nibbles, and Bytes Bit comes from joining binary and digit Bit is smallest unit of information Computer memory –KilobytesKilobytes –MegabytesMegabytes –GigabytesGigabytes Computer storage abilities are growing

18 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Review What is the primary difference between the decimal numbering system and the binary numbering system? The decimal system has numbers 0–9, and the binary system has 0 and 1

19 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Review What is the smallest unit of information in binary code? A bit

20 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Logic Gates AND gates OR gates NOT gates NAND gates NOR gates XOR gates XNOR gates

21 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. AND Gates Accepts high and low inputs (1 and 0) High and low outputs Output of 1 if all inputs are 1 If only one gate is on, circuit will not work Truth tables

22 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. AND Gates (Cont.)

23 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. AND Gates (Cont.) Valid logic highs and lows

24 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. OR Gates Output signal of 1 if either or both inputs is 1 When all inputs are 0, output is 0 Acts similar to two switches in parallel

25 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. OR Gates (Cont.) Valid logic highs and lows

26 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. NOT Gates Used to invert polarity of input signal –Also called invertersinverters If input is 1, output is 0 If input is 0, output is 1

27 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. NOT Gates (Cont.) Valid logic highs and lows

28 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. NAND Gates Made of an AND gate and a NOT gate Reverse of AND application Also called NOT AND gates

29 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. NAND Gates (Cont.) Valid logic highs and lows

30 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. NOR Gates Opposite of OR gate Made of OR and NOT gates Used to test for any kind of input No input will have output of 1

31 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. NOR Gates (Cont.) Valid logic highs and lows

32 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. XOR Gates Also called exclusive OR gatesexclusive OR gates Provide high output if any, but not all, inputs are logic high Provide low output if all inputs are logic high

33 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. XOR Gates (Cont.) Valid logic highs and lows

34 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. XNOR Gates Also called exclusive NOR gatesexclusive NOR gates XOR gate with inverted output High output only when all inputs are logic high or logic low

35 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Review Which gate has an output signal of 1 if either or both inputs is 1? OR gate

36 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Review Which gate provides high output if any, but not all, inputs are logic high, but provides a low output if all inputs are logic high? XOR gate

37 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Review Which gate is made of an AND and a NOT gate? NAND gate

38 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Review Which gate has an inverted output so it has a high output only when all inputs are logic high or logic low? XNOR

39 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Logic Families Traits of one logic family must match traits of another family when many digital ICs are used in one device Complementary metal-oxide semiconductor logic (CMOS)Complementary metal-oxide semiconductor logic (CMOS) Transistor-transistor logic (TTL)

40 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. CMOS Logic Circuits have good resistance to noise Use FETs Require small amounts of power Can be damaged by static electricity Worker and work surface must be grounded through high-resistance resistor

41 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. TTL Circuits work quickly Function from 20 megahertz to 60 megahertz Faster than CMOS ICs Require high power dissipation and high current Many gates can be placed in one TTL IC

42 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Review If many digital circuits are used in one device, how should logic families be treated? Traits of one logic family must match traits of another family

43 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Review Which of the two types of logic families can be easily damaged by static electricity? CMOS

44 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Digital Applications Logic probes Digital encoders and decodersencodersdecoders Digitized analog signals Flip-flops Counters

45 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Logic Probes Indicate a high or low signal using LEDs Connect to power supply of circuit being tested Equipped with a slide switch to select the logic family If both LEDs light, there is an invalid logic level voltage

46 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Digital Encoders and Decoders Electronic systems translate binary system into decimal system Analog-to-digital converters can change analog numbers to a digital number equivalent –Digital multimeter as example Can convert electrical pulses into binary numbers

47 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Digitized Analog Signals Digital signals representing sound waves or linear voltage Analog-to-digital encoders are used

48 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Flip-Flops Set-reset (R-S) flip-flops J-K flip-flops D flip-flops

49 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. R-S Flip-Flops When S is high, Q is high Output represents last input setting if both inputs are low Outputs are complementarycomplementary Clocked R-S flip-flops

50 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. J-K Flip-Flops Clock driven Retain output status when two inputs are low When both inputs are high, outputs toggle on and off

51 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. D Flip-Flops Do not require two inputs Q outputs toggle when input signal is received if clock signal is applied Output state of Q will not change without clock signal Output Qs are always complementary

52 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Counters Can carry and borrow Fabricated from individual flip-flops Available as integrated chips

53 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Decade Counters Can count based on ten Can be used to divide by ten Used as frequency dividers for oscilloscopes or in digital clocks

54 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Computerized Tomography (CT) Uses photomultiplier tubes, computer scans, and X-rays to produce digitized images of the body Photocathodes Dynodes Anode grid Gantry Contrast agent

55 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Review How can binary numbers be translated into the decimal system? Digital decoders

56 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Review What is a flip-flop? A semiconductor device that can assume one of two stable states

57 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Review What kind of flip-flop does not require two inputs? D flip-flop

58 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Review What does it mean if two outputs are complementary? When one output is high, the other is low

59 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. For Discussion Give examples of advantages integrated circuits have over transistors. What are the differences among the logic gates? Give examples of possible advances that will be made in the computer field in the next 25 years, based on what you have learned in this chapter.

60 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary AND gate –A logic gate that is used to determine the presence of yes signals or 1s. Binary –A number system having a base of 2, using only the symbols 0 and 1. Bit –One binary digit (0 or 1).

61 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Byte –Two binary nibbles, or eight binary bits. Clocked R-S flip-flop –A flip-flop in which the output changes when there is a change in the R or S input and a pulse appears at the clock input.

62 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Complementary –A principle behind the operation of a flip-flop that results in one high output when the other is low. Complementary metal-oxide semiconductor logic (CMOS) –A digital circuit arrangement that uses field- effect transistors for its logic circuits.

63 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Counter –Series of events that can be triggered by a pulse train or a lever. D flip-flop –Semiconductor device similar to the J-K flip- flop, except it does not require two inputs.

64 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Decade counter –A common digital counter that counts in base ten. Decimal system –A numbering system in which ten digits are available.

65 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Decoder –Part of a communications system that changes a coded message into an uncoded message. Encoder –Part of a communications system that changes the information source into coded form.

66 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Exclusive NOR gate –A logic gate that provides a logic high output (1) only if all inputs are logic high or logic low. Exclusive OR gate –A logic gate that provides a high output (1) whenever any, but not all, inputs are logic high.

67 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Flip-flop –A digital device based on the operation of combined logic gates. Gigabyte –A measure of computer memory, equal to 1,000,000,000 bytes.

68 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Intermediate range –In digital circuits, the area between value logic high and value logic low that acts as a buffer range. Also called invalid value range. Invalid value range –In digital circuits, the area between value logic high and value logic low that acts as a buffer range.

69 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Inverter –A gate that changes the polarity of an incoming signal in the output. J-K flip-flop –A clock-driven flip-flop, similar to the R-S flip- flop, except that it retains its output status when two lows are present at its inputs.

70 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Kilobyte –A measure of computer memory equal to 1000 bytes. Logic gate –An integrated circuit used mostly as a digital switching device.

71 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Megabyte –A measure of computer memory equal to 1,000,000 bytes. NAND gate –A negative AND logic gate. Nibble –One-half of a byte, or four bits. NOR gate –A negative OR logic gate.

72 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary NOT gate –An inverter that changes the polarity of an incoming signal in the output. OR gate –A logic gate that will provide an output signal if there is a signal on either of its inputs.

73 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Set-reset (R-S) flip-flop –A flip-flop in which outputs are complementary, but in which both inputs cannot be high. Transistor-transistor logic (TTL) –An arrangement of digital circuits using transistors to perform logic functions.

74 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Truth table –A binary table that explains the operation of digital logic circuits. Valid logic high –Operating voltage required for a digital circuit to be in the 1, or on, position. Voltage range is usually 2 to 5 volts.

75 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary Valid logic low –Operating voltage required for a digital circuit to be in the 0, or off, position. Voltage range is usually 0 to 1.5 volts. XNOR gate –A logic gate that provides a logic high output (1) only if all inputs are logic high or logic low.

76 © Goodheart-Willcox Co., Inc.Permission granted to reproduce for educational use only. Glossary XOR gate –A logic gate that provides a high output (1) whenever any, but not all, inputs are logic high.


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