06 Digital Circuits

Digital circuits¶

• combinational circuits
• sequential circuits

Applications of combinational circuits¶

1. Arithmetic and logic functions
2. adder
3. subtractor
4. comparator
5. PLD (Programmable Logic Device)
6. Data Transmission
7. multiplexer
8. de-multiplexer
9. encoder
10. decoder
11. code conversion
12. Binary
13. BCD
14. 7-Segment

Sequential Logic Circuit¶

output depends on present inputs and past outputs (feedback)

sequential circuit will have storage elements to store the past outputs so that they can be fed back to the input

therefore, sequential circuit can be expressed as a combinational circuit with storage and feedback element

flowchart LR
Inputs --> c[Combinational Circuit] --> Outputs --> s[Storage Element] --> c

States¶

• Present state

• Next state

Examples¶

1. counters
2. shift registers
3. sequence detector
4. function generator

Clock¶

is a periodic square pulse

has 3 features

1. rising(+ve) edge \(( \to )\) \((\uparrow)\) not ideal, but alright for trigger because it is only for a short duration, but requires power
2. level(neutral) edge — worst for trigger because large power required and duration is for \(t\) seconds
3. falling(-ve) edge \((\to)\) with a bubble \((\downarrow)\) best for trigger because it is only for a short duration and requires least power

always low logic design is the best as it requires the least power

Types of Sequential Circuits¶

1. +ve trigger/sensitive
2. Level trigger/sensitive
3. -ve trigger/sensitive

Storage elements¶

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