Datasheet LM208AH Datasheet (NSC)

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

18V and have sufficient supply rejection to use unregulat-

g

2V to

ed 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,

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

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

R1aR2

e

C

30 pF

O

TL/H/7759– 1

*Improves rejection of power supply

noise by a factor of ten.

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

TL/H/7759– 2

.

s

Feedforward Compensation

TL/H/7759– 3

C

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

TL/H/7759

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)

Input Voltage (Note 3)

g

10 mA

g

15V

Output Short-Circuit Duration Continuous

Operating Free Air Temperature Range

LM108A
LM208A

b

55§Ctoa125§C

b

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

80 300 V/mV

25§C, V

e

1.0 5.0 mV/

0.5 2.5 pA/

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

§

e

g

10V,

OUT

e

10 kX

L

s

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

A

40 V/mV

g

13

g

13.5 V

g

14 V

§

§

C

§

C

§

C

§

C

C

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

g

Differential Input Current (Note 2)

Input Voltage (Note 3)

10 mA

g

15V

Output Short-Circuit Duration Continuous

Operating Temperature Range 0§Ctoa70§C

b

Storage Temperature Range

65§Ctoa150§C

H-Package Lead Temperature

(Soldering, 10 sec.) 300

§

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

80 300 V/mV

2.0 5.0 mV/

2.0 10 pA/

e

g

10V,

OUT

e

10 kX

L

s

a

70§C, unless otherwise specified.

A

60 V/mV

g

13

g

14 V

g

14 V

C

§

C

§

C

§

C

§

C

§

C

§

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/
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

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.

TL/H/7759– 7

Order Number LM108AH, LM208AH or LM208AH

See NS Package Number H08C

Physical Dimensions inches (millimeters)

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)

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)

Molded Dual-In-Line Package (N)

Order Number LM308AN

NS Package Number N08E

LM108A/LM208A/LM308A Operational Amplifiers

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DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL
SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or 2. A critical component is any component of a life
systems which, (a) are intended for surgical implant support device or system whose failure to perform can
into the body, or (b) support or sustain life, and whose be reasonably expected to cause the failure of the life
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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