4. OPERATIONAL AMPLIFIERS CIRCUITS by Ulaby & Maharbiz All rights reserved. Do not copy or distribute. © 2013 National Technology and Science Press

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

not copy or distribute. © 2013 National

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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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


Tech Brief 5: IC FabricationAll rights reserved. Do

not copy or distribute. © 2013 National


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


Operational Amplifier “Op Amp”

Two input terminals, positive (noninverting) 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)


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


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


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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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


Noninverting Amplifier

021

R

v

R

vv non

so vR

RRv

2

21

spn vvv

(max) = Vcc

At node


Inverting Amplifier

0 pn vv


Example 4-2: Input Current Source

Relate output voltage to input current source


Summing Amplifier

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Example 4-3:

Solution:

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Difference Amplifier

Note negative gain of channel 1


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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Example 4-5: Elevation Sensor

Sensor Response

Desired Output

h = elevation, inversely proportional to air pressure


Example 4-6: Multiple Op-Amp Circuit


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


Instrumentation Amplifier

Highly sensitive differential amplifier

122

321

5

4 vvR

RRR

R

Rvo


Digital to Analog Converter

Converts digital value into analog voltage

4-digit example


Digital to Analog Converter

Represent digital value with analog voltage


MOSFET (Field Effect Transistor)

Active Device: Voltage Controlled Current Source

Gate voltage controls drain/source current


MOSFET Equivalent Circuit

Characteristic curves Idealized response


Example 4-9: MOSFET Amplifier

Given:

Determine


Load Line

You can use a “load line” to graphically determine Vout = VDS for a given Vin = VGS

RL

VDD

VDD/RD


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”


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


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


Example: Multisim Instruments


Multisim Table


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Multisim: MOSFET I-V Analyzer


Tech Brief 6: Display Technologies

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Tech Brief 6: Display Technologies

Digital Light Processing (DLP)


Summary


Documents

4. OPERATIONAL AMPLIFIERS CIRCUITS by Ulaby & Maharbiz All rights reserved. Do not copy or distribute. © 2013 National Technology and Science Press