Download Periodic Waveforms

Introduction
• Molecules: made up of atoms of individual elements.
• Atoms: made up of a nucleus surrounded by orbiting electrons.
• Nucleus: made up of protons and neutrons.
• Protons: have a positive charge which attract orbiting electrons,
which have a negative charge.
Introduction
• Electric current is when electrons flow from one atom to the next.
• Voltage is electrical potential energy.
• Ohm’s Law is a fundamental equation in electronics: V = R  I; voltage
across a component is equal to the current through it multiplied by its
resistance.
Atomic Structure
• Neutron: particle in nucleus of atom having no charge (neutral).
• Electron: negatively charged particle orbiting nucleus of atom.
• Orbital path: paths of electrons orbiting atom’s nucleus.
• Atomic number: number of protons in nucleus of atom.
Introduction
• Kirchhoff’s Current Law (KCL): explains why current entering a node
must equal current leaving node; current cannot be created or
destroyed.
• Kirchhoff’s Voltage Law (KVL): voltage supplied from one or more
sources must be the same amount as voltage dropped across one or
more circuit elements.
Kirchhoff’s Voltage and
Current Laws
• Figure 2.4: Two
resistors in series.
Figure 2.9: Two resistors
in parallel.
Breadboarding
• Breadboard: device with hidden interconnections on which to build
prototype circuit.
• Trace: copper line on circuit board connecting one component to
another; path for current to flow on circuit board.
Breadboarding
• Simulation: entering a schematic (drawing) of a circuit to test into a
computer program which calculates voltages and currents throughout
the circuit without physically building the circuit.
• Prototype: circuit built functionally the same as a circuit to test.
Introduction
• Digital electronics is based on the
combination and switching of logic levels.
• Physically, logic levels are represented by
voltages.
• Logic levels are usually specified as 0 or 1
(bits).
• Each logic level corresponds to a digit in
the binary (base 2) number system.
Introduction
• Time-varying digital waveforms:
o Periodic waveforms: repeat a pattern of
logic 1s and 0s.
o Aperiodic waveforms: do not repeat.
o Pulse waveforms: produce a momentary
variation from a constant logic level.
Digital Versus Analog Electronics
• Analog: physical, continuous quantity;
analog voltage or current can have any
value within a defined range.
• Digital: physical quantity by a series of
binary numbers; can have only specific
discrete values.
Digital Logic Levels
• Logic level: voltage level that represents a
defined digital state in an electronic circuit.
• Logic LOW (logic 0): lower of two voltages
in a digital system with two logic levels.
• Logic HIGH (logic 1): higher of two
voltages in digital system with two logic
levels.
Binary Inputs
• Most significant bit (MSB): leftmost bit in
binary number; largest positional multiplier.
• Least significant bit (LSB): rightmost bit of
binary number; smallest positional
multiplier.
• Truth table: list of output levels of a circuit
corresponding to all different input
combinations.
Decimal-to-Binary Conversion
• Sum of Powers of 2: convert decimal
number to binary by adding up powers of 2
by inspection, adding bits to fill up total
value of number.
• Repeated Division by 2: any decimal
number divided by 2 will leave a remainder
of 0 or 1.
Hexadecimal Numbers
• Hexadecimal number system: base-16
number system written with sixteen digits,
0–9, and A–F, with power-of-16 positional
multipliers.
• Hexadecimal (hex) numbers: primarily
used as shorthand form of binary notation.
Counting in Hexadecimal
Table 3.4: Hex Digits and Their Binary and Decimal
Equivalents.
Digital Waveforms
• Digital waveform: series of logic 1s and 0s
plotted as a function of time.
• Timing diagram: digital waveform, typically
with multiple signals on one plot.
Periodic Waveforms
• Periodic waveforms repeat same pattern
of HIGHs and LOWs over specified period
of time.
• Clock: special case of a symetrical,
periodic waveform with a specified
frequency.
• Time LOW (tl): time during one period that
waveform is in LOW state.
Periodic Waveforms
• Time HIGH (th): time during one period that
waveform is in HIGH state.
• Period (T): time required for periodic
waveform to repeat.
• Frequency (f): number of times per second
that periodic waveform repeats.
• Duty cycle (DC): fraction of total period that
digital waveform is in HIGH state.
Pulse Waveforms
• Pulse: variation of voltage from one logic
level to opposite level and back again.
• Rising edge: part of a pulse where logic
level is in transition from LOW to HIGH.
• Falling edge (trailing): part of pulse where
logic level is in transition from HIGH to
LOW.
Basic Logic Functions
Figure 4.1: Inverter Symbols
Figure 4.2: 2-Input AND Gate Symbol
Basic Logic Functions
Figure 4.6: 2-Input OR Gate Symbol
Figure 4.7: OR Function Represented
by Switches in Parallel
Basic Logic Functions
• Active Level: logic level defined as “ON” state for
particular circuit input or output (either HIGH or
LOW).
• Active LOW: active-LOW terminal considered “ON”
when in logic LOW state.
• Active HIGH: active-HIGH terminal considered
“ON” when in logic HIGH state.
Derived Logic Functions
Figure 4.12: 2-Input NAND Gate Symbol.
Derived Logic Functions
Figure 4.13: 2-Input NOR Gate Symbols.
Derived Logic Functions
Figure 4.18: Exclusive OR (XOR) Gate
Symbols
Figure 4.19: Exclusive NOR (XNOR)
Gate
DeMorgan’s Theorems and Gate
Equivalence
Figure 4.21: NAND Gate and DeMorgan Equivalent (positive and
negative NAND)
Logic Switches and LED Indicators
• LED (Light-Emitting Diode):
electronic device that conducts
current in one direction only and
illuminates when it is
conducting.
Figure 4.31: Light-Emitting Diode
(LED)
Enable and Inhibit Properties of Logic Gates
• Digital Signal (or Pulse Waveform): series of 0s and 1s plotted over
time.
• Enable: logic gate is enabled if it allows a digital signal to pass from an
input to the output in either true or complement form.
• Inhibit (or Disable): logic gate is inhibited if it prevents a digital signal
from passing from an input to the output.