LM308.PDF

December 1994

LM108/LM208/LM308 Operational Amplifiers

General Description

The LM108 series are precision operational amplifiers hav-

ing specifications a factor of ten better than FET amplifiers

over a b 55 § Cto a 125 § C temperature range.

The devices operate with supply voltages from g 2V to

g 20V and have sufficient supply rejection to use unregulat-

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 by-

pass capacitors unnecessary.

The low current error of the LM108 series makes possible

many designs that are not practical with conventional ampli-

fiers. In fact, it operates from 10 M X source resistances,

introducing less error than devices like the 709 with 10 k X

sources. Integrators with drifts less than 500 m V/sec and

analog time delays in excess of one hour can be made us-

ing capacitors no larger than 1 m F.

The LM108 is guaranteed from b 55 § Cto a 125 § C, the

LM208 from b 25 § Cto a 85 § C, and the LM308 from 0 § Cto

a 70 § C.

Features

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 m A, even in saturation

Y Guaranteed drift characteristics

Compensation Circuits

Standard Compensation Circuit

Alternate* Frequency Compensation

R1 CO

R1 a R2

C O e 30 pF

TL/H/7758±1

TL/H/7758±2

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

*Improves rejection of power supply noise by a factor of ten.

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

Feedforward Compensation

TL/H/7758±3

C 1995 National Semiconductor Corporation

TL/H/7758

RRD-B30M115/Printed in U. S. A.

C f t

Absolute Maximum Ratings

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

(Note 5)

LM108/LM208

LM308

Supply Voltage

g 20V

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 (LM108)

b 55 § Cto a 125 § C

0 § Cto a 70 § C

(LM208)

b 25 § Cto a 85 § C

Storage Temperature Range

b 65 § Cto a 150 § C

Lead Temperature (Soldering, 10 sec)

DIP

260 § C

H Package Lead Temp

(Soldering 10 seconds)

300 § C

Soldering Information

Dual-In-Line Package

Soldering (10 seconds)

260 § C

Small Outline Package

Vapor Phase (60 seconds) 215 § C

Infrared (15 seconds) 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

Condition

LM108/LM208

LM308

Units

Min Typ Max Min Typ Max

Input Offset Voltage

T A e 25 § C

0.7

2.0

7.5 mV

Input Offset Current

T A e 25 § C

0.05

0.2

Input Bias Current

T A e 25 § C

0.8

2.0

1.5

Input Resistance

T A e 25 § C

M X

Supply Current

T A e 25 § C

0.3

0.6

0.3

0.8 mA

Large Signal Voltage T A e 25 § C, V S e g 15V

V OUT e g 10V, R L t 10 k X

300

V/mV

Input Offset Voltage

3.0

10 mV

Average Temperature

Coefficient of Input

3.0

6.0

30 m V/ § C

Offset Voltage

Input Offset Current

0.4

1.5

Average Temperature

Coefficient of Input

0.5

2.5

2.0

pA/ § C

Offset Current

Input Bias Current

3.0

Supply Current

T A ea 125 § C

0.15

0.4

Gain R L t 10 k X

Output Voltage Swing V S e g 15V, R L e 10 k X g 13 g 14

V/mV

g 13 g 14

Gain

Large Signal Voltage V S e g 15V, V OUT e g 10V

Electrical Characteristics (Note 4) (Continued)

Parameter

Condition

LM108/LM208

LM308

Units

Min

Typ Max Min

Typ Max

Input Voltage Range

V S e g 15V

g 13.5

g 14

Common Mode

100

Rejection Ratio

Supply Voltage

Rejection Ratio

Note 1: The maximum junction temperature of the LM108 is 150 § C, for the LM208, 100 § C and for the LM308, 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 5V s V S s g 20V and b 55 § C s T A s a 125 § C, unless otherwise specified. With the LM208, however, all temperature

specifications are limited to b 25 § C s T A s 85 § C, and for the LM308 they are limited to 0 § C s T A s 70 § C.

Note 5: Refer to RETS108X for LM108 military specifications and RETs 108AX for LM108A military specifications.

Note 6: Human body model, 1.5 k X in series with 100 pF.

Schematic Diagram

TL/H/7758±8

Typical Performance Characteristics LM108/LM208

Input Currents

Offset Error

Drift Error

Closed Loop

Input Noise Voltage

Power Supply Rejection

Output Impedance

Voltage Gain

Output Swing

Supply Current

Open Loop

Large Signal

Voltage Follower

Frequency Response

Pulse Response

TL/H/7758±6

Typical Performance Characteristics LM308

Input Currents

Offset Error

Drift Error

Closed Loop

Input Noise Voltage

Power Supply Rejection

Output Impedance

Voltage Gain

Output Swing

Supply Current

Open Loop

Large Signal

Voltage Follower

Frequency Response

Pulse Response

TL/H/7758±7

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