LM108A,LM208A,LM308A
LM108A LM208A LM308A Operational Amplifiers
Literature Number: SNOSBS6A
LM108A/LM208A/LM308A Operational Amplifiers
Obsolete
General Description
The LM108/LM108A series are precision operational amplifiers having specifications about a factor of ten better than
FET amplifiers over their operating temperature range. In
addition to low input currents, these devices have extremely
low offset voltage, making it possible to eliminate offset adjustments, in most cases, and obtain performance approaching chopper stabilized amplifiers.
The devices operate with supply voltages from
g
18V and have sufficient supply rejection to use unregulated supplies. Although the circuit is interchangeable with and
uses the same compensation as the LM101A, an alternate
compensation scheme can be used to make it particularly
insensitive to power supply noise and to make supply bypass capacitors unnecessary.
The low current error of the LM108A series makes possible
many designs that are not practical with conventional amplifiers. In fact, it operates from 10 MX source resistances,
g
2V to
Compensation Circuits
Standard Compensation Circuit
introducing less error than devices like the 709 with 10 kX
sources. Integrators with drifts less than 500 mV/sec and
analog time delays in excess of one hour can be made using capacitors no larger than 1 mF.
The LM208A is identical to the LM108A, except that the
LM208A has its performance guaranteed over a
a
85§C temperature range, instead ofb55§Ctoa125§C.
The LM308A devices have slightly-relaxed specifications
and performances over a 0
Ctoa70§C temperature range.
§
Features
Y
Offset voltage guaranteed less than 0.5 mV
Y
Maximum input bias current of 3.0 nA over temperature
Y
Offset current less than 400 pA over temperature
Y
Supply current of only 300 mA, even in saturation
Y
Guaranteed 5 mV/§C drift
Alternate* Frequency Compensation
May 1989
b
25§Cto
LM108A/LM208A/LM308A Operational Amplifiers
R1 C
O
t
C
f
R1aR2
e
C
30 pF
O
**Bandwidth and slew rate are proportional to 1/Cf.
C
1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.
TL/H/7759
TL/H/7759– 1
Feedforward Compensation
*Improves rejection of power supply
noise by a factor of ten.
**Bandwidth and slew rate are proportional to 1/C
TL/H/7759– 3
TL/H/7759– 2
.
s
LM108A/LM208A Absolute Maximum Ratings
Obsolete
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
(Note 5)
Supply Voltage
Power Dissipation (Note 1) 500 mW
Differential Input Current (Note 2)
Input Voltage (Note 3)
Output Short-Circuit Duration Continuous
Operating Free Air Temperature Range
LM108A
LM208A
b
55§Ctoa125§C
b
g
20V
g
10 mA
g
15V
25§Ctoa85§C
Storage Temperature Range
Lead Temperature (Soldering, 10 sec.) (DIP) 260§C
Soldering Information
Dual-In-Line Package
Soldering (10 sec.) 260
Small Outline Package
Vapor Phase (60 sec.) 215
Infrared (15 sec.) 220
See An-450 ‘‘Surface Mounting Methods and Their Effect
on Product Reliability’’ for other methods of soldering surface mount devices.
ESD Tolerance (Note 6) 2000V
b
65§Ctoa150§C
Electrical Characteristics (Note 4)
Parameter Conditions Min Typ Max Units
Input Offset Voltage T
Input Offset Current T
Input Bias Current T
Input Resistance T
Supply Current T
Large Signal Voltage Gain T
Input Offset Voltage 1.0 mV
Average Temperature Coefficient
of Input Offset Voltage
Input Offset Current 0.4 nA
Average Temperature Coefficient
of Input Offset Current
Input Bias Current 3.0 nA
Supply Current T
Large Signal Voltage Gain V
Output Voltage Swing V
Input Voltage Range V
Common Mode Rejection Ratio 96 110 dB
Supply Voltage Rejection Ratio 96 110 dB
Note 1: The maximum junction temperature of the LM108A is 150§C, while that of the LM208A is 100§C. For operating at elevated temperatures, devices in the H08
package must be derated based on a thermal resistance of 160
package is 100
Note 2: The inputs are shunted with back-to-back diodes for overvoltage protection. Therefore, excessive current will flow if a differential input voltage in excess of
1V is applied between the inputs unless some limiting resistance is used.
Note 3: For supply voltages less than
Note 4: These specifications apply for
specifications are limited to
Note 5: Refer to RETS108AX for LM108AH and LM108AJ-8 military specifications.
Note 6: Human body model, 1.5 kX in series with 100 pF.
C/W, junction to ambient.
§
b
25§CsT
g
15V, the absolute maximum input voltage is equal to the supply voltage.
g
5VsV
s
85§C.
A
e
25§C 0.3 0.5 mV
A
e
25§C 0.05 0.2 nA
A
e
25§C 0.8 2.0 nA
A
e
25§C3070MX
A
e
25§C 0.3 0.6 mA
A
e
A
V
OUT
e
A
e
S
t
R
L
e
S
e
S
s
g
20V andb55§CsT
S
e
g
10V, R
g
15V,
S
t
10 kX
L
e
g
10V,
OUT
e
10 kX
L
s
125§C, unless otherwise specified. With the LM208A, however, all temperature
A
80 300 V/mV
1.0 5.0 mV/
0.5 2.5 pA/
40 V/mV
g
13
g
13.5 V
g
14 V
25§C, V
e
125§C 0.15 0.4 mA
g
15V, V
10 kX
g
15V, R
g
15V
C/W, junction to ambient, or 20§C/W, junction to case. The thermal resistance of the dual-in-line
§
§
§
C
§
C
§
C
§
C
C
2
LM308A Absolute Maximum Ratings
Obsolete
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
g
g
18V
10 mA
g
15V
Supply Voltage
Power Dissipation (Note 1) 500 mW
Differential Input Current (Note 2)
Input Voltage (Note 3)
Output Short-Circuit Duration Continuous
Operating Temperature Range 0§Ctoa70§C
Storage Temperature Range
H-Package Lead Temperature
(Soldering, 10 sec.) 300
b
65§Ctoa150§C
§
Lead Temperature (Soldering, 10 sec.) (DIP) 260
Soldering Information
Dual-In-Line Package
Soldering (10 sec.) 260
Small Outline Package
Vapor phase (60 sec.) 215
Infrared (15 sec.) 220
See An-450 ‘‘Surface Mounting Methods and Their Effect
on Product Reliability’’ for other methods of soldering surface mount devices.
ESD rating to be determined.
C
Electrical Characteristics (Note 4)
Parameter Conditions Min Typ Max Units
Input Offset Voltage T
Input Offset Current T
Input Bias Current T
Input Resistance T
Supply Current T
Large Signal Voltage Gain T
Input Offset Voltage V
Average Temperature Coefficient V
of Input Offset Voltage
Input Offset Current 1.5 nA
Average Temperature Coefficient
of Input Offset Current
Input Bias Current 10 nA
Large Signal Voltage Gain V
Output Voltage Swing V
Input Voltage Range V
Common Mode Rejection Ratio 96 110 dB
Supply Voltage Rejection Ratio 96 110 dB
Note 1: The maximum junction temperature of the LM308A is 85§C. For operating at elevated temperatures, devices in the H08 package must be derated based on
a thermal resistance of 160
ambient.
Note 2: The inputs are shunted with back-to-back diodes for overvoltage protection. Therefore, excessive current will flow if a differential input voltage in excess of
1V is applied between the inputs unless some limiting resistance is used.
Note 3: For supply voltages less than
Note 4: These specifications apply for
C/W, junction to ambient, or 20§C/W, junction to case. The thermal resistance of the dual-in-line package is 100§C/W, junction to
§
g
15V, the absolute maximum input voltage is equal to the supply voltage.
g
5VsV
A
A
A
A
A
A
V
OUT
S
S
S
R
L
S
S
s
g
15V and 0§CsT
S
e
25§C 0.3 0.5 mV
e
25§C 0.2 1 nA
e
25§C 1.5 7 nA
e
25§C1040MX
e
e
e
e
e
t
e
e
10 kX
25§C, V
25§C, V
e
g
g
15V, R
g
15V, R
g
15V, V
g
15V, R
g
15V
e
g
15V 0.3 0.8 mA
S
e
g
15V,
S
t
10V, R
10 kX
L
e
100X 0.73 mV
S
e
100X
S
e
g
10V,
OUT
e
10 kX
L
s
a
70§C, unless otherwise specified.
A
80 300 V/mV
2.0 5.0 mV/
2.0 10 pA/
60 V/mV
g
13
g
14 V
g
14 V
C
§
C
§
C
§
C
§
C
§
C
§
3
Typical Applications
Obsolete
Sample and Hold
²
Teflon, polyethylene or polycarbonate dielectric capacitor.
Worst case drift less than 2.5 mV/sec. TL/H/7759– 4
High Speed Amplifier with Low Drift and Low Input Current
TL/H/7759– 5
4
Application Hints
Obsolete
A very low drift amplifier poses some uncommon application
and testing problems. Many sources of error can cause the
apparent circuit drift to be much higher than would be predicted.
Thermocouple effects caused by temperature gradient
across dissimilar metals are perhaps the worst offenders.
Only a few degrees gradient can cause hundreds of microvolts of error. The two places this shows up, generally, are
the package-to-printed circuit board interface and temperature gradients across resistors. Keeping package leads
short and the two input leads close together helps greatly.
Resistor choice as well as physical placement is important
for minimizing thermocouple effects. Carbon, oxide film and
some metal film resistors can cause large thermocouple errors. Wirewound resistors of evanohm or manganin are best
since they only generate about 2 mV/
per. Of course, keeping the resistor ends at the same temperature is important. Generally, shielding a low drift stage
electrically and thermally will yield good results.
C referenced to cop-
§
Schematic Diagram
Resistors can cause other errors besides gradient generated voltages. If the gain setting resistors do not track with
temperature a gain error will result. For example, a gain of
1000 amplifier with a constant 10 mV input will have a 10V
output. If the resistors mistrack by 0.5% over the operating
temperature range, the error at the output is 50 mV. Referred to input, this is a 50 mV error. All of the gain fixing
resistor should be the same material.
Testing low drift amplifiers is also difficult. Standard drift
testing technique such as heating the device in an oven and
having the leads available through a connector, thermoprobe, or the soldering iron methodÐdo not work. Thermal
gradients cause much greater errors than the amplifier drift.
Coupling microvolt signal through connectors is especially
bad since the temperature difference across the connector
can be 50
gain setting resistor should be isothermal.
C or more. The device under test along with the
§
TL/H/7759– 6
5
Connection Diagrams
Obsolete
Metal Can Package
Dual-In-Line Package
Pin 4 is connected to the case.
**Unused pin (no internal connection) to allow for input anti-leakage guard
ring on printed circuit board layout.
Order Number LM108AH, LM208AH or LM208AH
See NS Package Number H08C
Physical Dimensions inches (millimeters)
TL/H/7759– 7
Top View
TL/H/7759– 8
Order Number LM108AJ-8, LM208AJ-8, LM308AJ-8,
LM308AM or LM308AN
See NS Package Number J08A, M08A or N08E
Order Number LM108AH, LM208AH or LM308AH
Metal Can Package (H)
NS Package Number H08C
6
Physical Dimensions inches (millimeters) (Continued)
Obsolete
Order Number LM108AJ-8, LM208AJ-8 or LM308AJ-8
Ceramic Dual-In-Line Package (J)
NS Package Number J08A
S.O. Package (M)
Order Number LM308AM
NS Package Number M08A
7
Physical Dimensions inches (millimeters) (Continued)
Obsolete
Molded Dual-In-Line Package (N)
Order Number LM308AN
NS Package Number N08E
LM108A/LM208A/LM308A Operational Amplifiers
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