Chapter 1

BASIC DIGITAL CONCEPTS

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 2

Lesson 1

Concepts of 1s and 0s

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 3

Outline

•• StateState• Positive Logic Examples• Negative Logic Examples• Logic Circuit Examples

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 4

Digital circuit

• An electronic circuit in which a state switches (changes) between two distinct circuit conditions when there are changes of input states or conditions

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 5

StateState

• A distinct condition of output or input voltages or currents or frequencies or phases of a circuit.

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 6

States 1 and 0States 1 and 0

• One of the state is represented by logic true or 1 or high or yes

• Other state is represented by logic falseor 0 or low or no

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 7

Example State 1

5 V

Ground Potential

R

LED ON

Switch ON

Ccompleteconnection

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 8

Example State 0

5 V

Ground Potential

R

LED OFF

Switch OFF

Complete connection

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 9

Example State Undefined

Incomplete connection Ground Potential

R

LED OFF

Switch ON

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 10

Example State Undefined

5 V

Ground Potential

R

LED Not Connected

Switch ON

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 11

We also learnt We also learnt

• Mere existence of condition 0V or no current or no signal or output or switch off, does not define state of a circuit as 0.

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 12

Outline

• State• Positive Logic Examples• Negative Logic Examples• Logic Circuit Examples

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 13

Logic 0: Low or -V or mA or frequency

Logic 1: High or +ve V or mA or frequency

Positive Logic

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 14

0

Positive Logic 1s and 0sPositive Logic 1s and 0s1

Maximum 5V Minimum 2.8 V

Maximum 0.8 VMinimum 0VMinimum 0V

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 15

0

Positive Logic 1s and 0sPositive Logic 1s and 0s1

Maximum +5V Minimum +3.3V

Maximum + 1.7 VMinimum 0V

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 16

0

Positive Logic 1s and 0sPositive Logic 1s and 0s1

Maximum + 20 mA Minimum + 16 mA

Maximum + 4 mAMinimum 0 mA

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 17

0

Positive Logic 1s and 0sPositive Logic 1s and 0s1

Maximum 1260 Hz frequency Minimum 1220 Hz frequency

Maximum 1060 Hz frequencyMinimum 1020 Hz frequency

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 18

Outline

• State• Positive Logic Examples•• Negative Logic Negative Logic ExamplesExamples• Logic Circuit Examples

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 19

Logic 1: Low or -ve V or mA or frequency

Logic 0: High V or mA or frequency

Negative Logic

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 20

0

Negative Logic 1s and 0sNegative Logic 1s and 0s1

Maximum −−−− 3 V Minimum −−−− 25 V

Maximum + 25 VMinimum Minimum +3V +3V

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 21

Outline

• State• Positive Logic Examples• Negative Logic Examples•• Logic Circuit ExamplesLogic Circuit Examples

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 22

0

A TTL circuit Logic 1s and 0sA TTL circuit Logic 1s and 0s1

Maximum 5V Minimum 2.8 V

Maximum 0.8 VMinimum 0VMinimum 0V

Output stage Transistor Off

Output stage Transistor ON

Output stage Transistor current 40 µµµµA

Output stage Transistor current 4 mA

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0

A CMOS circuit Logic 1s and 0sA CMOS circuit Logic 1s and 0s1

Maximum 5V Minimum 3.3 V

Maximum 1.6 VMinimum 0VMinimum 0V

Output stage MOSFET Off

Output stage MOSFET ON

Output stage MOSFET drain current 0 µµµµA at dc

Output stage MOSFET drain current 0 µµµµA at dc

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0

An RS232C circuit Logic 1s and 0sAn RS232C circuit Logic 1s and 0s1

Maximum -3V

Minimum -25 V

Maximum +25VMinimum 3VMinimum 3V

Output stage MOSFET ON

Output stage MOSFET OFF

Output stage MOSFET drain current 0 µµµµA at dc

Output stage MOSFET drain current 0 µµµµA at dc

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0

A Teletype loop circuit Logic 1s and 0sA Teletype loop circuit Logic 1s and 0s1

Maximum 20 mA Minimum +16mA

Maximum +25VMinimum 3VMinimum 3V

Output stage Coil current ON

Output stage Coil current OFF

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0

A Modem circuit Logic 1s and 0sA Modem circuit Logic 1s and 0s1

Maximum 1260 Hz

Minimum 1220 Hz

Maximum 1060 HzMinimum 1020Minimum 1020

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 27

Example State 1

5 V

Ground Potential

Modem Oscillator

Frequency 1240 Hz

Switch ON

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 28

Example State 0

5 V

Ground Potential

Modem Oscillator

Frequency 1040 Hz

Switch ON

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 29

Example State Undefined

5 V

Ground Potential

Modem Oscillator

Output < = 1000Hz

Switch ON

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 30

0

A Modulation circuit Logic 1s and 0sA Modulation circuit Logic 1s and 0s1

Phase angle + 90°°°°6666 45°°°°

Phase angle −−−−90°°°°6666 45°°°°

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Summary

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 32

• 1 represents a state of a circuit• 0 represents another state of circuit

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 33

• Different family of circuits have different discrete circuit conditions for 1 or 0 states. A condition may be defined by a range voltage, current, frequency or phase angle

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 34

We also learnt We also learnt

• Mere existence of condition 0V or no current or no signal or output or switch OFF, does not define state of a circuit as 0 or 1.

Ch01L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 35

We also learnt We also learnt

• Mere existence of connection to high voltage or high current or a signal or output or switch ON, does not define state of a circuit as 0.

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End of Lesson 1 on

Concepts of 1s and 0s

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