Datasheet
LT1124/LT1125
10
11245fe
APPLICATIONS INFORMATION
The LT1124 may be inserted directly into OP-270 sock-
ets. The LT1125 plugs into OP-470 sockets. Of course,
all standard dual and quad bipolar op amps can also be
replaced by these devices.
Matching Specifi cations
In many applications the performance of a system depends
on the matching between two op amps, rather than the
individual characteristics of the two devices. The three op
amp instrumentation amplifi er confi guration shown in this
data sheet is an example. Matching characteristics are not
100% tested on the LT1124/LT1125.
Some specifi cations are guaranteed by defi nition. For
example, 70µV maximum offset voltage implies that
mismatch cannot be more than 140µV. 112dB (= 2.5µV/V)
CMRR means that worst-case CMRR match is 106dB
Figure 1. Test Circuit for Offset Voltage and
Offset Voltage Drift with Temperature
(5µV/V). However, Table 1 can be used to estimate the
expected matching performance between the two sides of
the LT1124, and between amplifi ers A and D, and between
amplifi ers B and C of the LT1125.
Offset Voltage and Drift
Thermocouple effects, caused by temperature gradients
across dissimilar metals at the contacts to the input
terminals, can exceed the inherent drift of the amplifi er
unless proper care is exercised. Air currents should be
minimized, package leads should be short, the two input
leads should be close together and maintained at the same
temperature.
The circuit shown in Figure 1 to measure offset voltage
is also used as the burn-in confi guration for the LT1124/
LT1125, with the supply voltages increased to ±16V.
–
+
100*
50k*
50k*
15V
–15V
V
OUT
V
OUT
= 1000V
OS
*RESISTORS MUST HAVE LOW
THERMOELECTRIC POTENTIAL
1124/25 F01
Table 1. Expected Match
LT1124AC/AM
LT1125AC/AM
LT1124C/M
LT1125C/M
PARAMETER 50% YIELD 98% YIELD 50% YIELD 98% YIELD UNITS
V
OS
Match, ∆V
OS
LT1124 20 110 30 130 µV
LT1125 30 150 50 180 µV
Temperature Coeffi cient Match 0.35 1.0 0.5 1.5 µV/°C
Average Noninverting I
B
618725nA
Match of Noninverting I
B
722830nA
CMRR Match 126 115 123 112 dB
PSRR Match 127 118 127 114 dB