LT1037_15 Datasheet, PDF (9/16 Pages) Linear Technology – Low Noise, High Speed Precision Operational Amplifiers

LT1007/LT1037
APPLICATIONS INFORMATION
General
The LT1007/LT1037 series devices may be inserted
directly into OP-07, OP-27, OP-37 and 5534 sockets with
or without removal of external compensation or nulling
components. In addition, the LT1007/LT1037 may be
fitted to 741 sockets with the removal or modification of
external nulling components.
Offset Voltage Adjustment
The input offset voltage of the LT1007/LT1037 and its drift
with temperature, are permanently trimmed at wafer
testing to a low level. However, if further adjustment of
V_OS is necessary, the use of a 10kΩ nulling potentiometer
will not degrade drift with temperature. Trimming to a
value other than zero creates a drift of (V_OS/ 300)µV/°C,
e.g., if V_OS is adjusted to 300µV, the change in drift will be
1µV/°C (Figure 1).
The adjustment range with a 10kΩ pot is approximately
±2.5mV. If less adjustment range is needed, the sensitivity
and resolution of the nulling can be improved by using a
smaller pot in conjunction with fixed resistors. The ex-
ample has an approximate null range of ±200µV
(Figure 2).
INPUT
10k
1
2– 8
LT1007 ^{7 6}
3 +^LT1037
4
15V
OUTPUT
–15V
1007/37 F01
Figure 1. Standard Adjustment
1k
15V
4.7k
4.7k
1
2– 8
LT1007 ^{7 6}
3 +^LT1037
4
OUTPUT
–15V
1007/37 F02
Figure 2. Improved Sensitivity Adjustment
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 amplifier
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 to measure offset voltage is also used
as the burn-in configuration for the LT1007/LT1037, with
the supply voltages increased to ±20V (Figure 3).
50k*
15V
2–
7
100Ω*
3
LT1007
+^LT1037
4
50k*
–15V
6
V_OUT
V_OUT = 1000V_OS
*RESISTORS MUST HAVE LOW
THERMOELECTRIC POTENTIAL
1007/37 F03
Figure 3. Test Circuit for Offset Voltage and
Offset Voltage Drift with Temperature
Unity-Gain Buffer Application (LT1007 Only)
When R_F ≤ 100Ω and the input is driven with a fast, large-
signal pulse (>1V), the output waveform will look as
shown in the pulsed operation diagram (Figure 4).
During the fast feedthrough-like portion of the output, the
input protection diodes effectively short the output to the
input and a current, limited only by the output short-circuit
protection, will be drawn by the signal generator. With
R_F ≥ 500Ω, the output is capable of handling the current
requirements (I_L ≤ 20mA at 10V) and the amplifier stays
in its active mode and a smooth transition will occur.
R_F
–
+
LT1007
OUTPUT
2.8V/µs
1007/37 F04
Figure 4. Pulsed Operation
sn100737 100737fbs
9