1. 4. Operational Amplifiers
CIRCUITS by Ulaby & Maharbiz
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3. Tech Brief 5: IC Fabrication
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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.

4. Tech Brief 5: IC Fabrication
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Tech Brief 5: IC Fabrication

5. Tech Brief 5: IC Fabrication
Lithography: Defining spatial pattern
Photoresist: Polymer material that does not allow etching
or deposition of areas underneath it.
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6. Tech Brief 5: IC Fabrication
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Tech Brief 5: IC Fabrication

7. Tech Brief 5: IC Fabrication
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8. Tech Brief 5: IC Fabrication
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Tech Brief 5: IC Fabrication

9. Operational Amplifier “Op Amp”
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Operational Amplifier “Op Amp”
Two input terminals, positive (non- inverting) and negative (inverting)
One output
Power supply V+ , and
Op Amp with power supply not shown (which is how we usually display op amp circuits)
Op Amp showing power supply

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Inside The Op-Amp (741)

11. Gain Key important aspect of op amp: high voltage gain
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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 Circuit

13. Example 4-1: Op Amp Amplifier
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Example 4-1: Op Amp Amplifier
KCL at Node a:
Node a
KCL at Node b:
Node b
For infinite A:
= 5 =

14. Negative Feedback Feedback: return some of the output to the input
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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 input
Negative Feedback
No Feedback
Range of
Range of 5
Gain = 5
Range of
: ‒2 V to +2 V
: ‒10 mV to +10 mV
Gain = 1million
Range of

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Negative Feedback

16. Circuit Analysis With Ideal Op Amps
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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 voltage drop across op amp input
No current into op amp

17. Noninverting Amplifier
At node
(max) = Vcc
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18. Inverting Amplifier
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19. Example 4-2: Input Current Source
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Example 4-2: Input Current Source
Relate output voltage to input current source

20. Summing Amplifier
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21. Example 4-3:
Solution:
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22. Difference Amplifier Note negative gain of channel 1
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Difference Amplifier
Note negative gain of channel 1

23. “Buffers” Sections of Circuit
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Voltage Follower
“Buffers” Sections of Circuit
depends on both input and load resistors
is immune to input and load resistors
What is the op amp doing?

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25. Example 4-5: Elevation Sensor
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Example 4-5: Elevation Sensor
h = elevation, inversely proportional to
air pressure
Sensor Response
Desired Output

26. Example 4-6: Multiple Op-Amp Circuit
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Example 4-6: Multiple Op-Amp Circuit

27. Measurement Uncertainty
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Measurement Uncertainty
Direct Measurement v2
V0 = V2 ± 1% of V2
Thermistor
G = 1
± 1%
(T = 21°C)
21°C ± 0.21°C
Differential Measurement v2
G = 1 1%
Thermistor
V0 = (V2 ‒ V1) ± 1% of (V2 ‒ V1)
(T = 21°C)
1°C ± 0.01°C v1
Much better measurement uncertainty
Fixed Reference Temp = 20°C

28. Instrumentation Amplifier
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Instrumentation Amplifier
Highly sensitive differential amplifier

29. Digital to Analog Converter
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Digital to Analog Converter
Converts digital value into analog voltage
4-digit example

30. Digital to Analog Converter
Represent digital value with analog voltage
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31. MOSFET (Field Effect Transistor)
Active Device: Voltage Controlled Current Source
Gate voltage controls drain/source current
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32. MOSFET Equivalent Circuit
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MOSFET Equivalent Circuit
Characteristic curves
Idealized response

33. Example 4-9: MOSFET Amplifier
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Example 4-9: MOSFET Amplifier
Given:
Determine

34. Load Line You can use a “load line” to graphically determine
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Load Line
You can use a “load line”
to graphically determine
Vout = VDS for a given Vin = VGS
VDD/RD RL
VDD

35. Digital Circuit: MOSFET Inverter
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Digital Circuit: MOSFET Inverter
VDD = 15 V RL G S D ID 1 2 3 4 5 10 15 V GS =V in DS
out
VDD
Output
“High”
Logic 1
Output “High”
Logic 1
Output “Low”
Logic 0
Output
“Low”
Logic 0 In
Out 1 In
Out
Input “Low”
Input “High”

36. Read-Only Memory (ROM) Circuits
VREAD = 1
VBIT = 0100
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37. Another Digital Circuit Element: NAND
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Another Digital Circuit Element: NAND
No current flows through resistor, unless both A and B inputs turn their transistors on to “pull down” Vout
VDD A B
Out A B
Out 1
Vout A B
NAND gates can be used to build any binary logic function

38. Another Digital Circuit Element: NOR
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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
VDD A B
Out A B
Out 1
Vout A B
NOR gates can be used to build any binary logic function

39. Example: Multisim Instruments
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40. Multisim Table
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42. Multisim: MOSFET I-V Analyzer
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43. Tech Brief 6: Display Technologies
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44. Tech Brief 6: Display Technologies
Digital Light Processing (DLP)
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45. Summary
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