Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one...
-
date post
21-Dec-2015 -
Category
Documents
-
view
218 -
download
0
Transcript of Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one...
![Page 1: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/1.jpg)
Operational Amplifier
![Page 2: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/2.jpg)
Ideal OP Amp
1. iin=0, no current flow into op amp.
2. V+=V-
• Typically one end of op amp is connected to ground, therefore, V+=V-= 0V, virtual ground. Often V+ is connected to ground to avoid stability problem.
Circuit model
Two golden rules to perform calculations on op amps with negative feedback:
![Page 3: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/3.jpg)
Applications: building block for analog systems
• Amplifiers• Adders and Substractors• Integrators & Differentiators• Clock generators• Filters• Digital-to-analog converters
![Page 4: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/4.jpg)
Using op-amps
No flexibility
![Page 5: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/5.jpg)
Let’s build a circuit……noninverting amplifier
![Page 6: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/6.jpg)
When A is very large
Suppose A=106, R1=9R, R2=R
Gain: • determined by resistance ratio• insensitive to A, temperature, fab variation
![Page 7: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/7.jpg)
Why did this happen? Negative feedback
e.g. vIN=5V
Suppose I perturb the circuit (e.g. force v0 momentarily to 12V somehowStable point is when v+v-
Key: negative feedback portion of output fed to –ve input.
e.g. Car antilock brakes small corrections
![Page 8: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/8.jpg)
How to control a high-strung device
• Antilock brakes
![Page 9: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/9.jpg)
More op amp insights:
• Observe, under negative feedback,
• We also know • i+ 0• i- 0
Yield an easier analysis method (under negative feedback)
![Page 10: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/10.jpg)
Insightful analysis method: under negative feedback
![Page 11: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/11.jpg)
Voltage follower
has minimum effects on previous and next circuit.
Why is this circuit useful?
![Page 12: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/12.jpg)
Inverting Amplifier
0 inFs iii
F
out
S
S
Fs
R
v
R
v
ii
00
SS
Fout v
R
Rv
S
F
S
out
R
R
v
vGain
Feedback resistor, always to negative input
![Page 13: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/13.jpg)
Summing Amplifier: Add Circuit
FN iiii .....21
F
out
SN
SN
S
S
S
S
R
v
R
v
R
v
R
v ...
2
2
1
1
SN
SN
FS
S
FS
S
Fout v
R
Rv
R
Rv
R
Rv ...2
21
1
SNSSS
Fout vvv
R
Rv ...21
If RS1=RS2=…=RSN=RS
![Page 14: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/14.jpg)
Non-innverting Amplifier
S
in
vvv
i
vv
0 since
F
out
S
Fs
R
vv
R
v
ii
0
SS
F
S
Fout
vR
R
vR
Rv
1
1 _
S
F
S
out
R
R
v
vGain
Feedback resistor, always to negative input
![Page 15: Operational Amplifier. Ideal OP Amp 1.i in =0, no current flow into op amp. 2.V + =V - Typically one end of op amp is connected to ground, therefore,](https://reader035.fdocuments.us/reader035/viewer/2022062714/56649d575503460f94a36362/html5/thumbnails/15.jpg)
Differential Amplifier: Substractor
221
2 vRR
Rv
vv
21
1
21 0
R
vv
R
vv
ii
out
121
2 vvR
Rvout
Very useful if both signals are corrupted with noise: Electrocardiogram (EKG)