Texas Instruments LM108A, LM208A, LM308A Operational Manual

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