Intro to Digital Electronics. Classifications of Electronic Circuits Switching Circuits – by...
-
Upload
randolf-mclaughlin -
Category
Documents
-
view
213 -
download
0
Transcript of Intro to Digital Electronics. Classifications of Electronic Circuits Switching Circuits – by...
Intro to Digital Electronics
Classifications of Electronic Circuits
• Switching Circuits – by turning electricity on and off. – Figure 1– Known as the digital method.
• Regulating Circuits – controls intensity of current. – Figure 2– Known as the analog method
Figure 1 – Current is On or OffFigure 2 – Increase/Decrease Current
What’s Digital and AnalogDigital Analog
ComputersMicroprocessorsWatchesDisplays
Audio AmplifiersRadiosTelevisions – stations have recently gone digital
Why Digital?
• Digital electronics are simple, practical, and reliable.
• Combines simple switches and gates to create electrical functions.
• Digital means switching.– HI or 1 (one) or On– LO or 0 (zero) or Off
Truth Table of a Digital Circuit
• The operation of the circuit to the right is represented by the table.
• Describes switch and output status.
• Truth tables represent the operation of a circuit.
Truth Table
Switch Bulb
OPEN OFF (LO or 0)
CLOSED ON (HI or 1)
Timing Diagrams of a Digital Circuit
• Timing diagrams may also represent a digital circuit operation, in this case resistor voltage.
Logic Gates
Logic?
• Logic circuits are circuits that make decisions based on the inputs they receive.– Remember what the
digital signals can be?– 1 or 0; HI or LO; On or
Off
Logic Indicators
• Logic Indicator is a device that indicates the logic state (either HI or LO) of a certain point in a circuit.– Usually a LED
Boolean Algebra
• Conventional Algebra has 4 basic operations– Addition, subtraction, multiplication, division
• Boolean Algebra has 6 basic operations– AND, OR, NAND, NOR, NOT, YES
• Example: Using the AND Gate– Read as “A anded B equals Q”– Also read as A B = Q
• Try using the OR Gate:
QB
A
QB
A
The AND Logic Gate
A B Q1 1 11 0 00 1 00 0 0
When is the output of this
gate HI?
Boolean EquationA B = Q
The OR Logic Gate
A B Q1 1 11 0 10 1 10 0 0
When is the output of this
gate HI?
Boolean EquationA + B = Q
The NOT (Inverter) Logic Circuit
A Q1 00 1
The NOT logic circuit is also called
the “inverter”.
Boolean EquationA = Q
“A is equal to not Q”
Widely used in many circuits; NAND and NOR gates are created by adding inverters to AND and OR gates.
The YES Logic Circuit
A Q1 10 0
The input is the same as the output.
Also used as:Amplifiers – makes a weak
signal strong. Buffers – Isolates delicate
circuits
Boolean EquationA = Q
“A equals Q”
Transistors
3904 3906
The NOR Logic Gate
A B Q1 1 01 0 00 1 00 0 1
The result of this Gate is always
the opposite of an OR Gate.
Boolean EquationA + B = Q
The OR Gate vs. the NOR Gate
The OR Gate The NOR Gate
A B Q1 1 11 0 10 1 10 0 0
A B Q1 1 01 0 00 1 00 0 1
The NAND Logic Gate
A B Q1 1 01 0 10 1 10 0 1
The result of this Gate is always
the opposite of an AND Gate.
Boolean EquationA B = Q
The AND Gate vs. the NAND Gate
The AND Gate The NAND Gate
A B Q1 1 11 0 00 1 00 0 0
A B Q1 1 01 0 10 1 10 0 0