DigDesignCh01L1

Chapter 1

BASIC DIGITAL CONCEPTS

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

Lesson 1

Concepts of 1s and 0s


Outline

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


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


StateState

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


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


Example State 1

5 V

Ground Potential

R

LED ON

Switch ON

Ccompleteconnection


Example State 0

5 V

Ground Potential

R

LED OFF

Switch OFF

Complete connection


Example State Undefined

Incomplete connection Ground Potential

R

LED OFF

Switch ON



5 V

Ground Potential

R

LED Not Connected

Switch ON


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.


Outline

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


Logic 0: Low or -V or mA or frequency

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

Positive Logic


0

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

Maximum 5V Minimum 2.8 V

Maximum 0.8 VMinimum 0VMinimum 0V


0


Maximum +5V Minimum +3.3V

Maximum + 1.7 VMinimum 0V


0


Maximum + 20 mA Minimum + 16 mA

Maximum + 4 mAMinimum 0 mA


0


Maximum 1260 Hz frequency Minimum 1220 Hz frequency

Maximum 1060 Hz frequencyMinimum 1020 Hz frequency


Outline

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


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

Logic 0: High V or mA or frequency

Negative Logic


0

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

Maximum −−−− 3 V Minimum −−−− 25 V

Maximum + 25 VMinimum Minimum +3V +3V


Outline

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


0

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



Output stage Transistor Off

Output stage Transistor ON

Output stage Transistor current 40 µµµµA

Output stage Transistor current 4 mA


0

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



Output stage MOSFET Off

Output stage MOSFET ON

Output stage MOSFET drain current 0 µµµµA at dc



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




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


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


Example State 1

5 V

Ground Potential

Modem Oscillator

Frequency 1240 Hz

Switch ON


Example State 0

5 V

Ground Potential

Modem Oscillator

Frequency 1040 Hz

Switch ON



5 V

Ground Potential

Modem Oscillator

Output < = 1000Hz

Switch ON


0

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

Phase angle + 90°°°°6666 45°°°°

Phase angle −−−−90°°°°6666 45°°°°


Summary


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


• 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



• 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.



• 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.


End of Lesson 1 on

Concepts of 1s and 0s


THANK YOU

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DigDesignCh01L1