Download Engineering Lecture1: Logic Circuits & Basic

Engineering Lecture1:
Logic Circuits &
Concepts about basic
Electrical Engineering Devices
by Christin Sander
Overview
1) Logic Circuits
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Analogue vs Digital
Binary Numbers
Logic Gates
Boolean Algebra
Flip-Flops & Clocks
Counters
Data Storage
2) Electrical Engineering
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Overview of Transistors
Amplifiers
Operational Amplifiers
Analogue versus Digital
Analogue:
Digital:
ANALOGUE signals
vary in a continuous way,
can take any values
DIGITAL signals
represent information as a
sequence of discrete
varying physical quantities,
encode values into binary
numbers (0 or 1)
Analogue to Digital Conversion
In nature, signals normally occur in an
analogue way
 To convert them into a digital signal, a
threshold value is selected.
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 For
values below the threshold: 0
 For values above the threshold: 1
Binary Numbers
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Decimal Number System
The decimal number system is the base 10 number system
Uses 10 different symbols (0,1,2,…..9)
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In General, any number system can be used
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Binary Number System
The binary number system is the base 2 number system
Uses 2 different symbols (0 and 1)
A BInary digiT("BIT") in each position
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Binary logic circuits are useful for making controllers
A binary system can also represent numbers of any magnitude
Logic circuits can be realised which will perform arithmetical
operations on these binary numbers
This is the principle behind almost all digital calculators and
computers
Logic Gates
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Electronic circuits with one
or more input wires and one
output wire
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The voltage on the output
depends on the voltages on
the inputs
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The relationship between
inputs and output is a
logical function, determined
by the circuit arrangement
inside the gate.
Circuit
(made up of
transistors
used as
switches)
Logical Functions
Boolean Algebra
Flip-flops
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D Flip-flop
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Divide-by-2-circuit
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Ripple-Down Counter
J-K Flip-flop
Q+ indicates the value of Q after the next clock pulse
If J and K are different, Q takes on the value of J
If J and K are both 0, Q remains unchanged
If J and K are both 1, Q changes to its inverse (it "toggles")
Information from J and K is read in on the rising edge of the clock, and is
translated into action at the Q outputs on the FALLING edge of the clock
Synchronous Counter
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Synchronous Counter
(8-bits)
Data Register
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A circuit which can store temporarily all bits of a
binary number
A 3-bit register
(a typical personal computer will have
several 16-bit and 32-bit data registers
in its arithmetic unit)
Storage Devices: ROM
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A ROM cell
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Typical m-ROM device
Transistors
Small input current controls a
large output current
Can act as a switch if in saturation
or cut-off region
Amplifiers
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An amplifier is a device that accepts a small
signal and outputs a larger signal that generally
matches the waveform characteristics of the
input
It amplifies the input signal
Factors affecting amplification
 Gain: Relationship
 Efficiency
 Bandwidth
 Settling
 Noise
time
of input and output signal
Operational Amplifiers
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An opamp is a device that
takes an analogue signal
and amplifies it
Output voltage depends on
difference of input voltage
Applications:
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Analogue to digital converters
Filters
Comparators