lt1002amj Linear Technology Corporation, lt1002amj Datasheet - Page 10

• Manufacturer Part Number: lt1002amj
• Description: Dual, Matched Precision Operational Amplifier
• Manufacturer: Linear Technology Corporation

LT1002
APPLICATIONS
Advantages of Matched Dual Op Amps In many applica-
tions the performance of a system depends on the match-
ing between two operational amplifiers rather than the
individual characteristics of the two op amps. Two or three
op amp instrumentation amplifiers, tracking voltage refer-
ences and low drift active filters are some of the circuits
requiring matching between two op amps.
The well-known triple op amp configuration illustrates
these concepts. Output offset is a function of the differ-
ence between the offsets of the two halves of the LT1002.
This error cancellation principle holds for a considerable
number of input referred parameters in addition to offset
voltage and its drift with temperature. Input bias current
will be the average of the two non-inverting input currents
(I
the offset current of the instrumentation amplifier. The
difference between the inverting input currents (I
cause errors flowing through R1, R2, and R3. Common-
mode and power supply rejections will be dependent only
on the match between the two amplifiers (assuming
perfect resistor matching).
The concepts of common mode and power supply rejec-
tion ratio match ( CMRR and PSRR) are best demon-
strated with a numerical example:
Assume CMRR
and CMRR
then CMRR = 0.25 V/V or 132dB;
if CMRR
then CMRR = 1.75 V/V or 115dB.
Clearly, the LT1002, by specifying and guaranteeing all of
these matching parameters, can significantly improve the
performance of matching dependent circuits.
10
B
+
). The difference between these two currents (I
B
= – 0.75 V/V which is still 122.5dB,
B
= + 0.75 V/V or 122.5dB,
A
= + 1.0 V/V or 120dB,
U
INFORMATION
U
W
U
OS
OS
–
) will
+
) is
INPUT
INPUT
Trim R8 for gain
Trim R9 for DC common mode rejection
Trim R10 for AC common mode rejection
Typical performance of the instrumentation amplifier:
Input offset voltage = 25 V
Input bias current = 0.7nA
Input resistance = 200 G
Input offset current = 0.6nA
Input noise = 0.5 V p-p
Power bandwidth (V
–
+
–
–
1/2 LT1002
+
1/2 LT1002
+
B
A
Three Op Amp Instrumentation Amplifier
R1
10k
1%
R2
10k
1%
R3
2.1k
1%
0
R8
200
= 10V) = 80kHz
100
100
1%
R5
1%
R4
C1
100pF
R10
100k
R7
9.76k
1%
R9
200
–
+
LT1037
GAIN = 1000
10k
1%
R6
OUTPUT
1002 TA07
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