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“Op-Amp”Operational Amplifier
• Non Inverting Amplifier• Inverting Amplifier• Adder
– (and Subtractor using an Inverter)
• Differential Amplifier• Integrator• Differentiator
Op-Amp name derives from early usage of these elements in performing mathematical operations in analog computers.
Three Ways to Examine Op-Amp Behavior
• Consider as an Ideal Op-Amp Component
• Consider as a Feedback Model and Examine Behavior
• Perform Conventional Circuit Analysis
“Op-Amp”Operational Amplifier
• Non Inverting Amplifier• Inverting Amplifier• Adder
– (and Subtractor using an Inverter)
• Differential Amplifier• Integrator• Differentiator
Op-Amp name derives from early usage of these elements in performing mathematical operations in analog computers.
Common Mode Rejection Ratio
vicm
v2
v1
vi1 vi2vid / 2
vid / 2
v2
v1
Original Inputs Model of inputs with common-mode and differential-mode
components
cmA
ACMRR where A is the differential
mode gain and Acm is the common mode gain
dBA
ACMRR
cmdB log20
Ideally: CMRR Typically: 60 dB CMRR 120 dB
Common Mode Rejection RatioCMRR
The Maximum Power Transfer Theorem simply states, the maximum amount of power will be dissipated by a load resistance when that load resistance is equal to the Thevenin/Norton resistance of the network supplying the power.
To create the Thevenin Equivalent Circuit we need:
1. Value of the Thevenin Voltage Source
2. Value of the Thevenin Resistance
Input and Output Impedances of
Noninverting Op-amp Configuration
The unity gain buffer input impedance is much higher
than the op-amp input impedance Rd. The amplifier output impedance is much smaller than the op-amp
output impedance Ro.
aiR
aoR+
Rdii
Ro
RL CL
ioAvd
vd
vo
vi
+
ARARR
ARARR
ooao
ddai
/)1/(
)1(
Instrumentation Amplifier
121
2
3
4 21 vvR
R
R
Rvv refout
vout
R3
v1
R2
R3
v2
R1
R2
R4
R4
vref
1
2
3
4
12
21R
R
R
R
vv
vvG refout
Instrumentation Amplifier Example
Burr-Brown INA118
Parameters: kRRkRRR G 60 25 4321
ININrefoout VvVvvVv 12 Ref
GIN
o
R
kVG
501
VV
Ref
IN
If RG 49.9,
G 1 50,00049.9
1,003
Gain:
Instrumentation Amp (cont.)A feedback network may also be included with the instrumentation amplifier.
vout
R3
v1
R2
R3
vdiff = v2 - v12R1
R2
R4
R4
R
C
RCs
Gs
sV
sV
diff
out
1
v2