LT1002 Datasheet, PDF (9/16 Pages) Linear Technology – Dual, Matched Precision Operational Amplifier

LT1002
APPLICATIONS INFORMATION
Test Circuit for Offset Voltage and its Drift with Temperature
*50k
+15V
3–
14 (7)
(10)
13 (6)
100Ω *
1_{/2 LT1002}
V_O
4+
(11)
50k *
12 (5)
–15V
*RESISTORS MUST HAVE LOW
THERMOELECTRIC POTENTIAL.
V_O = 1000 V_OS
1002 TA05
0.1µF
100kΩ
10Ω
–
1_{/2 LT1002}
+^A
DEVICE
UNDER
TEST
0.1Hz to 10Hz Noise Test Circuit
The device under test should be warmed up for three
minutes and shielded from air currents. Turn the device
180° to measure the noise of side B.
2kΩ
4.7 µF
VOLTAGE GAIN = 50,000
+
1_{/2 LT1002}
B
–
100k
24.3k
0.1 µF
4.3k
2.2µF
22µF
SCOPE
×1
R_IN = 1MΩ
110k
1002 TA06
This circuit is also used as burn-in configuration for the
LT1002, with supply voltages increased to ±20V.
(Peak to Peak noise measured in 10 Sec interval)
Unless proper care is exercised, thermocouple effects,
caused by temperature gradients across dissimilar metals
at the contacts to the input terminals, can exceed the
inherent drift of the amplifier. Air currents should be
minimized, package leads should be short, the two input
leads should be as close together as possible and main-
tained at the same temperature.
Power supplies
The LT1002 is specified over a wide range of power supply
voltages from ±3V to ±18V. Operation with lower supplies
is possible, down to ±1.2V (two Ni-Cad batteries). How-
ever, with ±1.2V supplies, the device is stable only in
closed loop gains of + 2 or higher (or inverting gain of one
or higher).
Channel Separation
This parameter is defined as the ratio of the change in input
offset voltage of one amplifier to the change in output
voltage of the other amplifier causing the offset change.
At low frequencies the LT1002’s channel separation is an
almost unmeasurable 148dB. As frequency increases, pin
to pin capacitance of the package, between the output of
one amplifier and the inputs of the other, becomes domi-
nant. Since these pins are non-adjacent, the capacitance is
only 0.02pF. To maintain the LT1002’s excellent channel
separation at higher frequencies, the socket and PC board
capacitances should be minimized.
The V+ supply terminals are completely independent and
may be powered by separate supplies if desired (this
approach, however, would sacrifice the advantages of the
power supply rejection ratio matching). The V– supply
terminals are both connected to the common substrate
and must be tied to the same voltage. Both V – pins should
be used.
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