LT1008CH Linear Technology, LT1008CH Datasheet - Page 8

• Manufacturer Part Number: LT1008CH
• Description: IC PREC OPAMP UNIVERSAL TO-5-8
• Manufacturer: Linear Technology

Specifications of LT1008CH

• Amplifier Type: General Purpose
• Number Of Circuits: 1
• Slew Rate: 0.2 V/µs
• Current - Input Bias: 30pA
• Voltage - Input Offset: 30µV
• Current - Supply: 380µA
• Voltage - Supply, Single/dual (±): ±2 V ~ 18 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Through Hole
• Package / Case: TO-5-8
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Output Type: -
• Current - Output / Channel: -
• -3db Bandwidth: -
• Gain Bandwidth Product: -

APPLICATIO S I FOR ATIO
LT1008
Achieving Picoampere/Microvolt Performance
In order to realize the picoampere—microvolt level accu-
racy of the LT1008, proper care must be exercised. For
example, leakage currents in circuitry external to the op
amp can significantly degrade performance. High quality
insulation should be used (e.g., Teflon
of all insulating surfaces to remove fluxes and other
residues will probably be required. Surface coating may be
necessary to provide a moisture barrier in high humidity
environments.
Board leakage can be minimized by encircling the input
circuitry with a guard ring operated at a potential close to
that of the inputs: in inverting configurations the guard
ring should be tied to ground, in noninverting connections
to the inverting input at Pin 2. Guarding both sides of the
printed circuit board is required. Bulk leakage reduction
depends on the guard ring width. Nanoampere level leak-
age into the compensation terminals can affect offset
voltage and drift with temperature.
Microvolt level error voltages can also be generated in the
external circuitry. Thermocouple effects caused by tem-
perature gradients across dissimilar metals at the con-
tacts to the input terminals can exceed the inherent drift of
the amplifier. Air currents over device leads should be
minimized, package leads should be short, and the two
input leads should be as close together as possible and
maintained at the same temperature.
8
REFERENCE ONLY—OBSOLETE PACKAGE
OUTPUT
V
V
–
+
U
5
6
4
7
GUARD
U
8
COMPENSATION
3
1
W
2
TM
, Kel-F); cleaning
1008 AI01
U
The LT1008 is specified over a wide range of power supply
voltages from ±2V to ±18V. Operation with lower supplies
is possible down to ±1.2V (two Ni-Cad batteries).
Noise Testing
The 0.1Hz to 10Hz peak-to-peak noise of the LT1008 is
measured in the test circuit shown. The frequency re-
sponse of this noise tester indicates that the 0.1Hz corner
is defined by only one zero. The test time to measure 0.1Hz
to 10Hz noise should not exceed 10 seconds, as this time
limit acts as an additional zero to eliminate noise contribu-
tions from the frequency band below 0.1Hz.
A noise voltage density test is recommended when mea-
suring noise on a large number of units. A 10Hz noise
voltage density measurement will correlate well with a
0.1Hz to 10Hz peak-to-peak noise reading since both
results are determined by the white noise and the location
of the 1/f corner frequency.
Current noise is measured in the circuit shown and calcu-
lated by the following formula where the noise of the
source resistors is subtracted.
Test Circuit for Offset Voltage and Its Drift with Temperature
100Ω*
i
50k*
n
=
⎡
⎣ ⎢
e
2
100Ω
no
2
3
40
–
+
–
LT1008
M
50k*
(
–15V
820
Ω ×
15V
10M*
10M*
*METAL FILM
7
4
nV
100
10M*
10M*
6
)
2
⎤
⎦ ⎥
2
3
1 2
10k
/
–
+
V
LT1008
O
*RESISTORS MUST HAVE LOW
THERMOELECTRIC POTENTIAL
THIS CIRCUIT IS ALSO USED AS
THE BURN-IN CONFIGURATION
FOR THE LT1008 WITH SUPPLY
VOLTAGES INCREASED TO ±20V
V
O
= 1000V
6
OS
1008 AI04
e
no
1008 AI02
1008fb