Transcript Interfacing Devices - ECM

Interfacing Devices
Chapter 2
Objectives
• Identify the schematic diagrams, describe
the operations, and calculate the outputs of
the comparator, inverting, summing,
noninverting, and difference operational
amplifiers (op amps)
• Identify the schematic diagrams of the
integrator and differentiator op amps and
draw the output waveforms they produce
when various input signals are applied
Objectives (cont’d.)
• Given applied input signals, indicate the
resulting output of the digital comparator
device
• Describe the wave-shaping capability and
operating characteristics of a Schmitt
trigger
• Determine how optoelectronic devices are
switched and explain the isolation function
they perform
Objectives (cont’d.)
• Explain the operation of analog-to-digital
and digital-to-analog converters, determine
their resolution, and make the proper
wiring connections to their integrated
circuit packages
• Assemble monostable and astable
multivibrators using a 555 monolithic
integrated circuit and use calculations to
determine their output
Fundamental Operational
Amplifiers
• Op amps
– uA741: one of the most popular
• Operational amplifier comparator
• Inverting operational amplifier
– Control gain using feedback
Fundamental Operational
Amplifiers
• Summing amplifier
– Two or more inputs are tied together and then
applied to an input lead of an op amp
FIGURE 2-5 Inverting summing amplifier
Fundamental Operational
Amplifiers
• Noninverting amplifier
– Equation used to determine the gain:
– Output voltage:
• Difference operational amplifier
– Finds the algebraic difference between two
input voltages
Signal Processors
• Devices that change or modify signals
applied to inputs
• Integrator operational amplifier
– Continuously increases its gain over a period
of time
• Differentiator operational amplifier
– Produces an output proportional to the rate of
change of the input signal
Signal Processors (cont’d.)
• Wave-shaping Schmitt trigger
– Device that produces rectangular wave signals
– Operation: three time periods
FIGURE 2-10b Schmitt trigger
Comparator Devices
• Function: produce an output error signal
that is determined by the difference
between the two inputs
• Magnitude comparator
– Compare two binary numbers
– 4-bit magnitude comparator
• Connect several to compare larger numbers
Optoelectronic Interface Devices
• Pass electrical signals from one element to
another by means of light energy and
semiconductors
– Light source: usually a semiconductor light
emitting diode (LED)
• Photodiode
– PN-junction device that operates in the
reverse-bias mode
Optoelectronic Interface Devices
(cont’d.)
• Phototransistor
– Depends on a light source for its operation
• Photo SCR
– Light-activated SCR, or LASCR
– Usually activated by light rather than a gate
voltage that draws gate current
Optoelectronic Interface Devices
(cont’d.)
• Photo triac
– Bidirectional device designed to switch AC
signals and pass current in both directions
• Optocoupler
– Package does not allow light to enter
• Optoisolator
– No electrical connection between the emitter
and the detector
Digital-to-Analog Converters
• Convert digital signals representing binary
numbers into proportional analog voltages
• Resolution
– Number of equal divisions into which a DAC
divides the reference voltage
• Integrated-circuit digital-to-analog
converter
– Example: 8-bit DAC0808
Analog-to-Digital Converters
• Converts analog input voltages into
proportional digital number
• Successive-approximation register (SAR)
– Circuit used to operate at high speeds
• Integrated-circuit analog-to-digital
converter
– Example: ADC0804
Timing Devices
• Produce rectangular signals referred to as
square-wave signals
• Monostable multivibrators
– Produce single pulse signals
– Example: 555 monostable multivibrator
• Astable multivibrators
– Produce continuous pulse signals
– Example: 555 astable multivibrator