ece 4991 electrical and electronic circuits chapter 8
TRANSCRIPT
ECE 4991 Electrical and Electronic ECE 4991 Electrical and Electronic CircuitsCircuits
Chapter 8Chapter 8
2
Where are we?Where are we?• Chapter 2 - The basic concepts and practice at
analyzing simple electric circuits with sources and resistors
• Chapter 3 – More harder networks to analyze and the notion of equivalent circuits
• Chapter 4 – Capacitors and inductors added to the mix
• Chapter 5 – Analyzing transient situations in complex passive networks
• Chapter 8 – New subject – the wonders of operational amplifiers as system elements
• Chapter 9 – Introduction to semiconductors – the basics and diodes – more network analysis
• Chapter 10 – Bipolar junction transistors and how they work – now you can build your own op amp
3
What’s Important in What’s Important in Chapter 8Chapter 8
1. Definitions2. Op Amp Basics3. Inverting Amplifiers4. Summing Amplifiers5. Non-inverting Amplifiers6. Voltage Followers7. Diff Amps8. Integrators9. Differentiators
4
1. Definitions1. Definitions
• Operational Amplifier
• Open-loop
• Feedback
• Inverting (input)
• Non-inverting (input)
• Open-loop voltage gain
5
2. Op Amp Basics2. Op Amp Basics• An operational amplifier is an IC
“engine” that can support many applications
• Defining characteristics– Amplifies difference between two input
voltage– Extremely high gain– Extremely high input resistance– Extremely low output resistance
6
Diagramming an Op AmpDiagramming an Op Amp
+ Pwr
_ Pwr
OutputNon-inverting
Input
Inverting Input
+
_
7
Design AssumptionsDesign Assumptions
Two main design assumptions for op amp applications using negative feedback
1. Zero input current
2. Input voltages forced to be equal
8
3. Inverting Amplifier3. Inverting Amplifier• + input grounded• Input signal to (–) input through RS
• Output fed back to (–) input through RF
• Gain = - RF/RS
+
_
9
Inverting Amplifier Inverting Amplifier PracticePractice
• Design an inverting amplifier with a gain of - 250
+
_
10
Inverting Amplifier Inverting Amplifier PracticePractice
• Given the following resistors to work with – 1KΩ, 1KΩ, 3KΩ, 20KΩ, 30KΩ – design an inverting amp with gain -40
+
_
11
4. Summing Amplifier4. Summing Amplifier• + input grounded• Several input signals to (–) input through RS’s• Output fed back to (–) input through RF
• Vout = - (RF / RSi) vsi
+
_
12
Summing Amplifier Summing Amplifier PracticePractice
• Design an amplifier with
Vout = - 50 (v1 + v2 + v3)
+
_
13
Summing Amplifier Summing Amplifier PracticePractice
• Design an amplifier with
Vout = - (20v1 +30v2 + 40v3)
+
_
14
5. Non-Inverting Amplifiers 5. Non-Inverting Amplifiers • Ground the (-) input through RS
• Signal input to + input through any R• Output fed back to (-) input through RF
• Gain is 1 + RF / RS
+
_
15
Non-Inverting Amplifier Non-Inverting Amplifier Practice Practice
• Design a non-inverting amp with gain = 10
+
_
16
Non-Inverting Amplifier Non-Inverting Amplifier Practice Practice
• Resistor collection is 20Ω, 50Ω, 100Ω, 100Ω, 300Ω, 300Ω, 500Ω
• Design a non-inverting amplifier with a gain of 5
+
_
17
6. Voltage Follower 6. Voltage Follower • Output fed back directly to (-) input • Signal input directly to + input • Vout = vS
+
_
18
What’s a Voltage Follower What’s a Voltage Follower For?For?
• Op amp input impedance very high
• Op amp output impedance very low
• Voltage followers buffer sensitive circuits or circuit elements
• Also used for driving speakers, long cables, etc
19
7. Differential Amplifiers 7. Differential Amplifiers
• V1 input fed to (-) input through R1
• V2 input fed to + input through a different R1
• Output tied back to (-) input through R2
• + input tied to ground through R2
• Vout = (R2/R1) (V2 – V1)
+
_
20
Differential Amplifier Differential Amplifier Practice Practice
• Design a diff amp with Vout = 50 (V2 – V1)
+
_
21
Differential Amplifier Differential Amplifier Practice Practice
• Design a diff amp with Vout = 200 sin t – 600 cos 3t
+
_
22
Differential Amplifier Differential Amplifier Practice Practice
• Design a diff amp with Vout = 40 sin t – 10 V1
+
_
23
8. Integrating Amplifiers 8. Integrating Amplifiers
• Signal input fed to (-) input through RS
• Output tied back to (-) input through CF
• + input tied to ground
• Vout = - (1/RSCF) VS dt
+
_
24
Integrating Amplifier Practice Integrating Amplifier Practice
• VS = 4 sin t, RS = 100 , CF = 50 F
• Vout = ?
+
_
25
Integrating Amplifier Practice Integrating Amplifier Practice
• Vout = - 200 t4 Volts
• VS = ?, RS = 1K, CF = ?
+
_
26
9. Differentiating Amplifiers 9. Differentiating Amplifiers
• Signal input fed to (-) input through CS
• Output tied back to (-) input through RF
• + input tied to ground
• Vout = - RFCS dVS/dt
+
_
27
Differentiating Amplifier Differentiating Amplifier PracticePractice
• Vout = - RFCS dVS/dt
• Design a differentiating amplifier with Vout = 30 sin t
+
_
28
Differentiating Amplifier Differentiating Amplifier PracticePractice
• Vout = - RFCS dVS/dt
• VS = 25 sin 2t, RF = 100, CS = 10 F
• Vout = ?
+
_
29
Op Amp PracticeOp Amp Practice
+
_
30
Op Amp PracticeOp Amp Practice
+
_
31
Op Amp PracticeOp Amp Practice
+
_
32
Op Amp PracticeOp Amp Practice
+
_
33
Op Amp PracticeOp Amp Practice
+
_
34
Op Amp PracticeOp Amp Practice
+
_