Upload
fitzgerald-emerson
View
40
Download
1
Tags:
Embed Size (px)
DESCRIPTION
Operational Amplifiers. Instructor: Chia-Ming Tsai Electronics Engineering National Chiao Tung University Hsinchu, Taiwan, R.O.C. Contents. Introduction Operational Amplifiers (OP AMPs) Ideal OP AMP Inverting AMP Noninverting AMP Summing AMP Difference AMP Cascaded OP AMP Circuits - PowerPoint PPT Presentation
Citation preview
Operational Amplifiers
Instructor: Chia-Ming TsaiElectronics Engineering
National Chiao Tung UniversityHsinchu, Taiwan, R.O.C.
Contents• Introduction
• Operational Amplifiers (OP AMPs)
• Ideal OP AMP
• Inverting AMP
• Noninverting AMP
• Summing AMP
• Difference AMP
• Cascaded OP AMP Circuits
• Applications
Introduction
• The op amp is a basic building block for performing mathematical operations such as summation, amplification, integration, and differentiation
• The concept of virtual short between the differential inputs of the op amp is extremely important for circuit analysis
OP AMPs
• Complex circuit networks consisting of transistors, resistors, capacitors, and diodes
Cont’d
12
12
210 (KCL)
vvAAvv
vvv
iiiii
do
d
Equivalent circuit of an op amp
+
_
Cont’dParameter Typical
rangeIdeal value
Open-loop gain, A
105 to 108
Input resistance, Ri
105 to 1013
Output resistance, Ro
10 to 100
0
Supply voltage, VCC
5 to 24 V
Slope = A
Example
? Find
50
102
1026
5
so
o
i
vv
R
R
A
short virtualare inputs alDifferenti
0 V 20
9999699.1
2, & 1 nodeat KCL Applying
1
v
v
v
s
o
Ideal OP AMP• Infinite open-loop voltage gain: A • Infinite input resistance: Ri
• Zero output resistance: Ro 0
• v1 = v2 (virtual short) assumed for analysis
Inverting AMP
The equivalent circuit
f
oi
R
vv
R
vvii
1
1
121
1, nodeat KCL Applying
if
o vR
Rv
vv
1
21
0
amp, op idealan For
(feedback resistor)
Example: I-to-V Converters
Riv so
i1 i2
i3
a
2
3
1
31 1
R
R
R
RRiv so
Noninverting AMP
f
o
R
vv
R
vii
v
1
1
121
1
0
, nodeat KCL Applying
if
o
i
vR
Rv
vvv
1
21
1
amp, op idealan For
Voltage Follower• Conditions: Rf = 0 or R1 = or both
• Unity gain: Av = 1
• Useful as a buffer amp due to its very high Ri and very low Ro
Summing AMP
3
3
2
2
1
1321
, nodeat KCL Applying
R
v
R
v
R
viiii
a
3
32
21
1
vR
Rv
R
Rv
R
Rv fff
o
Difference AMP
43
2
21
1
, nodeat KCL Applying
, nodeat KCL Applying
R
v
R
vv
b
R
vv
R
vv
a
bb
oaa
121
2
4321
11
22
43
21
1
2
, If
1
1
vvR
Rv
RRRR
vR
Rv
RR
RR
R
Rv
vv
o
o
ba
Cascaded OP AMP Circuits
321
and 0
amps, op idealFor
AAAA
RR oi
Applications: DAC[V1 V2 V3 V4] Decimal - Vo
0000 0 0
0001 1 0.125
0010 2 0.25
0011 3 0.375
0100 4 0.5
0101 5 0.625
0110 6 0.75
0111 7 0.875
1000 8 1.0
1001 9 1.125
1010 10 1.25
1011 11 1.375
1100 12 1.5
1101 13 1.625
1110 14 1.75
1111 15 1.875
MSB: most significant bitLSB: least significant bit
Digital-to-Analog Converter (DAC)
Applications:Instrumentation Amplifier (IA)
Gv
vo
R
RA
vvAv
21
12
Cont’d• Characteristics of IA
– Voltage gain adjustable by RG
– Very high Ri and very low Ro
– The differential voltage is amplified and the common-mode voltage is rejected