Datasheet LM108MW8, LM108AWG-883, LM108AW-MLS, LM108AJ-883, LM108AH-883 Datasheet (NSC)

TL/H/7759

LM108A/LM208A/LM308A Operational Amplifiers

May 1989

LM108A/LM208A/LM308A Operational Amplifiers

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

2V to

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,

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

b

25§Cto

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

Compensation Circuits

Standard Compensation Circuit

C

f

t

R1 C

O

R1aR2

C

O

e

30 pF

TL/H/7759– 1

**Bandwidth and slew rate are proportional to 1/Cf.

**Bandwidth and slew rate are proportional to 1/C

s

.

Alternate* Frequency Compensation

*Improves rejection of power supply

noise by a factor of ten.

TL/H/7759– 2

Feedforward Compensation

TL/H/7759– 3

C

1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.

LM108A/LM208A Absolute Maximum Ratings

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
(Note 5)

Supply Voltage

g

20V

Power Dissipation (Note 1) 500 mW

Differential Input Current (Note 2)

g

10 mA

Input Voltage (Note 3)

g

15V

Output Short-Circuit Duration Continuous

Operating Free Air Temperature Range

LM108A

b

55§Ctoa125§C

LM208A

b

25§Ctoa85§C

Storage Temperature Range

b

65§Ctoa150§C

Lead Temperature (Soldering, 10 sec.) (DIP) 260§C

Soldering Information

Dual-In-Line Package

Soldering (10 sec.) 260

§

C

Small Outline Package

Vapor Phase (60 sec.) 215

§

C

Infrared (15 sec.) 220

§

C

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

Electrical Characteristics (Note 4)

Parameter Conditions Min Typ Max Units

Input Offset Voltage T

A

e

25§C 0.3 0.5 mV

Input Offset Current T

A

e

25§C 0.05 0.2 nA

Input Bias Current T

A

e

25§C 0.8 2.0 nA

Input Resistance T

A

e

25§C3070MX

Supply Current T

A

e

25§C 0.3 0.6 mA

Large Signal Voltage Gain T

A

e

25§C, V

S

e

g

15V,

80 300 V/mV

V

OUT

e

g

10V, R

L

t

10 kX

Input Offset Voltage 1.0 mV

Average Temperature Coefficient

1.0 5.0 mV/

§

C

of Input Offset Voltage

Input Offset Current 0.4 nA

Average Temperature Coefficient

0.5 2.5 pA/

§

C

of Input Offset Current

Input Bias Current 3.0 nA

Supply Current T

A

e

125§C 0.15 0.4 mA

Large Signal Voltage Gain V

S

e

g

15V, V

OUT

e

g

10V,

40 V/mV

R

L

t

10 kX

Output Voltage Swing V

S

e

g

15V, R

L

e

10 kX

g

13

g

14 V

Input Voltage Range V

S

e

g

15V

g

13.5 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

§

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 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

g

15V, the absolute maximum input voltage is equal to the supply voltage.

Note 4: These specifications apply for

g

5VsV

S

s

g

20V andb55§CsT

A

s

125§C, unless otherwise specified. With the LM208A, however, all temperature

specifications are limited to

b

25§CsT

A

s

85§C.

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.

2

LM308A Absolute Maximum Ratings

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.

Supply Voltage

g

18V

Power Dissipation (Note 1) 500 mW

Differential Input Current (Note 2)

g

10 mA

Input Voltage (Note 3)

g

15V

Output Short-Circuit Duration Continuous

Operating Temperature Range 0§Ctoa70§C

Storage Temperature Range

b

65§Ctoa150§C

H-Package Lead Temperature

(Soldering, 10 sec.) 300

§

C

Lead Temperature (Soldering, 10 sec.) (DIP) 260

§

C

Soldering Information

Dual-In-Line Package

Soldering (10 sec.) 260

§

C

Small Outline Package

Vapor phase (60 sec.) 215

§

C

Infrared (15 sec.) 220

§

C

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.

Electrical Characteristics (Note 4)

Parameter Conditions Min Typ Max Units

Input Offset Voltage T

A

e

25§C 0.3 0.5 mV

Input Offset Current T

A

e

25§C 0.2 1 nA

Input Bias Current T

A

e

25§C 1.5 7 nA

Input Resistance T

A

e

25§C1040MX

Supply Current T

A

e

25§C, V

S

e

g

15V 0.3 0.8 mA

Large Signal Voltage Gain T

A

e

25§C, V

S

e

g

15V,

80 300 V/mV

V

OUT

e

g

10V, R

L

t

10 kX

Input Offset Voltage V

S

e

g

15V, R

S

e

100X 0.73 mV

Average Temperature Coefficient V

S

e

g

15V, R

S

e

100X

2.0 5.0 mV/

§

C

of Input Offset Voltage

Input Offset Current 1.5 nA

Average Temperature Coefficient

2.0 10 pA/

§

C

of Input Offset Current

Input Bias Current 10 nA

Large Signal Voltage Gain V

S

e

g

15V, V

OUT

e

g

10V,

60 V/mV

R

L

t

10 kX

Output Voltage Swing V

S

e

g

15V, R

L

e

10 kX

g

13

g

14 V

Input Voltage Range V

S

e

g

15V

g

14 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

§

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

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

g

15V, the absolute maximum input voltage is equal to the supply voltage.

Note 4: These specifications apply for

g

5VsV

S

s

g

15V and 0§CsT

A

s

a

70§C, unless otherwise specified.

3

Typical Applications

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

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/

§

C referenced to cop­per. 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.

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

§

C or more. The device under test along with the

gain setting resistor should be isothermal.

Schematic Diagram

TL/H/7759– 6

5

Connection Diagrams

Metal Can Package

TL/H/7759– 7

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

Dual-In-Line Package

TL/H/7759– 8

Top View

Order Number LM108AJ-8, LM208AJ-8, LM308AJ-8,

LM308AM or LM308AN

See NS Package Number J08A, M08A or N08E

Physical Dimensions inches (millimeters)

Metal Can Package (H)

Order Number LM108AH, LM208AH or LM308AH

NS Package Number H08C

6

Physical Dimensions inches (millimeters) (Continued)

Ceramic Dual-In-Line Package (J)

Order Number LM108AJ-8, LM208AJ-8 or LM308AJ-8

NS Package Number J08A

S.O. Package (M)

Order Number LM308AM

NS Package Number M08A

7

LM108A/LM208A/LM308A Operational Amplifiers

Physical Dimensions inches (millimeters) (Continued)

Molded Dual-In-Line Package (N)

Order Number LM308AN

NS Package Number N08E

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failure to perform, when properly used in accordance support device or system, or to affect its safety or
with instructions for use provided in the labeling, can effectiveness.
be reasonably expected to result in a significant injury
to the user.

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a

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