AMP03
System Design
Requirement
Suggested Op Amp
For A1 and A2
AMP03
E
E
2
Source Impedance Low, Need Low
Voltage Noise Performance
OP27, OP37
OP227 (Dual Matched)
OP270 (Dual)
OP271
R
1
OP80EJ
OP470
OP471
I
0
LOAD
I
= (E – E )/R
0
1
2
Source Impedance High
(RS ≥ 15 kΩ). Need Low Current
Noise
OP80
OP41
OP43
OP249
OP97
Figure 27. Differential Input Voltage-to-Current Converter
for Low IOUT. OP80EJ Maintains 250 fA Max Input Current,
Allowing IO to Be Less Than 1 pA
AMP03
–IN E
1
A
1
Require Ultrahigh Input Impedance OP80
R
2
OP97
OP41
OP43
E
OUTPUT
0
R
R
1
2
A
Need Wider Bandwidth and High
Speed
OP42
OP43
OP249
2
+IN E
2
E
= (1 + 2R /R ) (E – E )
2 1 2 1
0
Figure 28. Suitable Instrumentation Amplifier Requirements
Can Be Addressed by Using an Input Stage Consisting of A1,
A2, R1 and R2. The Following Matrix Suggests a Suitable
Amplifier.
REV. E
–7–
ADI [ ADI ]
