4. operational amplifiers circuits by ulaby & maharbiz all rights reserved. do not copy or...
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4. OPERATIONAL AMPLIFIERS
CIRCUITS by Ulaby & Maharbiz
All rights reserved. Do not copy or distribute. © 2013 National Technology and Science Press
All rights reserved. Do
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Technology and Science Press
Tech Brief 5: IC Fabrication
Wafer: Thin slice of semiconductor material with highly polished surface
Processed wafer is cut into many dies or chips.
Lithography: Defining spatial pattern
Photoresist: Polymer material that does not allow etching or deposition of areas underneath it.
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National Technology and Science Press
Tech Brief 5: IC FabricationAll rights reserved. Do not
copy or distribute. © 2013 National Technology
and Science Press
Lithography: Defining spatial pattern
Photoresist: Polymer material that does not allow etching or deposition of areas underneath it.
Tech Brief 5: IC Fabrication
All rights reserved. Do not copy or distribute. © 2013 National Technology and Science Press
Tech Brief 5: IC FabricationAll rights reserved. Do
not copy or distribute. © 2013 National
Technology and Science Press
Tech Brief 5: IC Fabrication All rights reserved. Do not copy or distribute.
© 2013 National Technology and Science
Press
Tech Brief 5: IC Fabrication All rights reserved. Do not copy or distribute. © 2013 National
Technology and Science Press
Operational Amplifier “Op Amp”
Two input terminals, positive (non- inverting) and negative (inverting)
One output Power supply V+ , and
Op Amp showing power supply
Op Amp with power supply not shown (which is how we usually display op amp circuits)
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Inside The Op-Amp (741)All rights reserved. Do not copy or distribute. © 2013 National Technology and Science Press
Gain
Key important aspect of op amp: high voltage gain
Output , A is op-amp gain (or open-loop gain) – different from circuit gain G
Linear response
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Equivalent CircuitAll rights reserved. Do not copy or distribute. © 2013 National Technology and Science Press
Example 4-1: Op Amp Amplifier
KCL at Node a:
KCL at Node b:
2
210
R
RR
v
vG
s
For infinite A:
= 4.999975
= 5
Node a
Node b
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Negative Feedback Feedback: return some of the output to the
input Negative feedback decreases input signal Achieves desired circuit gain, with wide
range for inputNegative Feedback No Feedback
5CC
s
Vv sAvv 0
A
Vv CCs Range of Range of5
Gain = 5 Range of : ‒2 V to +2 VGain = 1millionRange of : ‒10 mV to +10 mV
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Negative FeedbackAll rights reserved. Do not copy or distribute. © 2013 National Technology and Science Press
Circuit Analysis With Ideal Op Amps
Use nodal analysis as before, but with “golden rules”
N Do not apply KCL at op amp output
No current into op amp
No voltage drop across op amp input
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Noninverting Amplifier
021
R
v
R
vv non
so vR
RRv
2
21
spn vvv
(max) = Vcc
At node
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Inverting Amplifier
0 pn vv
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Example 4-2: Input Current Source
Relate output voltage to input current source
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Summing Amplifier
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Example 4-3:
Solution:
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Difference Amplifier
Note negative gain of channel 1
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Voltage Follower
“Buffers” Sections of Circuit
What is the op amp doing?
depends on both input and load resistors
is immune to input and load resistors
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Technology and Science Press
Example 4-5: Elevation Sensor
Sensor Response
Desired Output
h = elevation, inversely proportional to air pressure
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Example 4-6: Multiple Op-Amp Circuit
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Measurement Uncertainty
(T = 21°C)
v2 V0 = V2 ± 1% of V2
21°C ± 0.21°CG = 1± 1%
G = 1 1%
v2
(T = 21°C)
Thermistor
Thermistor
v1
Fixed Reference Temp = 20°C
V0 = (V2 ‒ V1) ± 1% of (V2 ‒ V1)
1°C ± 0.01°C
Direct Measurement
Differential Measurement
Much better measurement uncertainty
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Instrumentation Amplifier
Highly sensitive differential amplifier
122
321
5
4 vvR
RRR
R
Rvo
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Digital to Analog Converter
Converts digital value into analog voltage
4-digit example
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Digital to Analog Converter
Represent digital value with analog voltage
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MOSFET (Field Effect Transistor)
Active Device: Voltage Controlled Current Source
Gate voltage controls drain/source current
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MOSFET Equivalent Circuit
Characteristic curves Idealized response
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Example 4-9: MOSFET Amplifier
Given:
Determine
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Load Line
You can use a “load line” to graphically determine Vout = VDS for a given Vin = VGS
RL
VDD
VDD/RD
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Digital Circuit: MOSFET Inverter
VDD = 15 V
RL
G
S
D ID
DSout VV GSin VV
Output“High”Logic 1
Output“Low”Logic 0
In Out
0 1
1 0 Input “Low”
In Out
VDD
0 1 2 3 4 50
5
10
15
VGS
=Vin
VD
S=
Vou
t
Output “Low”Logic 0
Output “High”Logic 1
Input “High”
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Read-Only Memory (ROM) Circuits
VREAD = 1VBIT = 0100
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Another Digital Circuit Element: NAND
A B Out
0 0 1
0 1 1
1 0 1
1 1 0
A
BOut
VDD
A
Vout
B
No current flows through resistor, unless both A and B inputs turn their transistors on
to “pull down” Vout
NAND gates can be used to build any binary logic function
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Another Digital Circuit Element: NOR
Current will flow if either A or B inputs turn their transistors on to “pull down” Vout
A B Out
0 0 1
0 1 0
1 0 0
1 1 0
A
BOut
A
VDD
Vout
B
NOR gates can be used to build any binary logic function
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Example: Multisim Instruments
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Multisim Table
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Multisim: MOSFET I-V Analyzer
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Tech Brief 6: Display Technologies
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Tech Brief 6: Display Technologies
Digital Light Processing (DLP)
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Summary
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