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EE445:Industrial Electronics
Outline
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Introduction
Some application
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Comparators
Integrators & Differentiators
Summing Amplifier
Digital-to-Analog (D/A) Converter
Difference Amplifier
Instrumentation Amplifiers
Audio Amplifier
Operational Amplifier (Op-Amp)
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Op-amp – A high-gain dc amplifier that has high
input impedance and low output impedance.
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The inverting (–) input and noninverting (+) input are signal
inputs.
The +V and –V inputs are supply voltage inputs.
Differential Amplifier
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Differential amplifier – A circuit that amplifies the
difference between two input voltages.
The op-amp signal inputs are connected to a
differential amplifier.
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The circuit amplifies the difference between the voltages at
its inverting (-) and noninverting (+) inputs.
Negative Feedback
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Negative feedback – A type of feedback in which the
feedback signal is 180° out of phase with the input signal.
Positive Feedback
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Positive feedback – A type of feedback in which the
feedback signal is in phase with the input signal.
Inverting Amplifier Operation
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The negative feedback path in the inverting amplifier:
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Reduces voltage gain (from its open-loop value).
Increases bandwidth (relative to its open-loop value).
Noninverting Amplifier Operation
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The negative feedback path in the noninverting amplifier:
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Reduces voltage gain (from its open-loop value).
Increases bandwidth (relative to its open-loop value).
Comparators
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Comparator – A circuit used to compare two
voltages.
Comparators are typically used in conjunction with
digital circuits.
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A digital circuit is one designed to respond to alternating dc
voltage levels.
Comparator Operation
Level Detector
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Level detector – Another name for a comparator used
to compare an input voltage to a fixed dc reference
voltage.
Setting the Reference Level
Vref
R2
 V
R1  R2
Smoke Detector: A Comparator
Application
Integrators
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Integrator – A circuit whose output is proportional to
the area of the input waveform.
RC Integrator
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An ideal RC integrator would produce the triangular
(ramp) waveform.
The practical RC integrator produces the exponential
waveform.
Op-Amp Integrator
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The op-amp provides a constant-current source for
the capacitor, causing it to charge at a linear rate.
Differentiators
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Differentiator – A circuit whose output is proportional
to the rate of change of its input signal.
Summing Amplifiers
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Summing amplifier – An op-amp circuit that produces
an output proportional to the sum of its input
voltages.
Vout
 V1 V2 V3 
 - R f  
 
 R1 R2 R3 
General-Class Equation
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General-class equation – An equation derived for a
summing amplifier that is used to predict the circuit
output for any combination of input voltages.
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Determine the Rf / R ratio for each branch.
Represent each branch as the product of its resistance ratio
and input voltage.
Write the equation as the sum of these products.
Summing Amplifier Analysis
Rf
R1
Rf
R2
Rf
R3
Rf
R4
V1  V1
V2  0.2V2
V3  0.1V3
V4  0.05V4
- Vout  V1  0.2V2  0.1V3  0.05V4
Digital-to-Analog (D/A) Converter
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Digital-to-analog (D/A) converter – A circuit that
converts digital circuit outputs to equivalent analog
voltages.
- Vout  V1  0.5V2  0.25V3  0.125V4
Averaging Amplifier
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Averaging amplifier – A summing amplifier that
provides an output proportional to the average of the
input voltages.
- Vout
V1  V2  V3

3
Difference Amplifier
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Difference amplifier – A summing amplifier that
provides an output proportional to the difference
between two input voltages. Also called a subtractor.
Vout
R3

(V2 - V1 )
R1
Instrumentation Amplifiers
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Instrumentation amplifier – A circuit used to amplify
low-level signals in process control and measurement
applications.
ACL
2R
 1
RG
Audio Amplifier
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Audio amplifier – The final audio stage in
communications receivers, used to drive the
speakers.
Thank You
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