The LM108 series are precision operational amplifiers having specifications a factor of ten better than FET amplifiers
b
over a
55§Ctoa125§C temperature range.
The devices operate with supply voltages fromg2V to
g
20V 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 LM108 series makes possible
many designs that are not practical with conventional amplifiers. In fact, it operates from 10 MX source resistances,
Compensation Circuits
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 LM108 is guaranteed from
LM208 from
a
70§C.
b
25§Ctoa85§C, and the LM308 from 0§Cto
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 mA, even in saturation
Y
Guaranteed drift characteristics
December 1994
b
55§Ctoa125§C, the
LM108/LM208/LM308 Operational Amplifiers
Standard Compensation Circuit
**Bandwidth and slew rate are proportional to 1/C
R1 C
O
t
C
f
R1aR2
e
C
30 pF
O
TL/H/7758– 1
f
Feedforward Compensation
Alternate* Frequency Compensation
*Improves rejection of power supply noise by a factor of ten.
**Bandwidth and slew rate are proportional to 1/C
s
TL/H/7758– 2
TL/H/7758– 3
C
1995 National Semiconductor CorporationRRD-B30M115/Printed in U. S. A.
TL/H/7758
Page 2
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/LM208LM308
Supply Voltage
g
20V
g
18V
Power Dissipation (Note 1)500 mW500 mW
Differential Input Current (Note 2)
Input Voltage (Note 3)
g
10 mA
g
15V
g
g
10 mA
15V
Output Short-Circuit DurationContinuousContinuous
Operating Temperature Range (LM108)
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)
ParameterCondition
Input Offset VoltageT
Input Offset CurrentT
Input Bias CurrentT
Input ResistanceT
Supply CurrentT
Large Signal VoltageT
GainV
e
25§C0.72.02.07.5mV
A
e
25§C0.050.20.21nA
A
e
25§C0.82.01.57nA
A
e
25§C30701040MX
A
e
25§C0.30.60.30.8mA
A
A
OUT
e
25§C, V
e
g
S
10V, R
e
g
15V
t
10 kX
L
Input Offset Voltage3.010mV
Average Temperature
Coefficient of Input3.0156.030mV/
Offset Voltage
Input Offset Current0.41.5nA
Average Temperature
Coefficient of Input0.52.52.010pA/
Offset Current
Input Bias Current3.010nA
Supply CurrentT
Large Signal VoltageV
GainR
Output Voltage SwingV
ea
125§C0.150.4mA
A
e
g
15V, V
S
t
10 kX
L
e
g
15V, R
S
OUT
L
e
e
g
10 kX
10V
LM108/LM208LM308
MinTypMaxMinTypMax
Units
5030025300V/mV
2515V/mV
g
g
13
14
g
g
13
14V
C
§
C
§
2
Page 3
Electrical Characteristics (Note 4) (Continued)
ParameterCondition
e
Input Voltage RangeV
g
15V
S
Common Mode
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
dual-in-line 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 RETS108X for LM108 military specifications and RETs 108AX for LM108A military specifications.
Note 6: Human body model, 1.5 kX in series with 100 pF.
C/W, junction to ambient.
§
g
15V, the absolute maximum input voltage is equal to the supply voltage.
g
5VsV
S
25§CsT
s
85§C, and for the LM308 they are limited to 0§CsT
A
b
s
g
20V andb55§CsT
LM108/LM208LM308
MinTypMaxMinTypMax
g
13.5
g
14V
8510080100dB
80968096dB
C/W, junction to ambient, or 20§C/W, junction to case. The thermal resistance of the
§
s
a
125§C, unless otherwise specified. With the LM208, however, all temperature
Teflon polyethylene or
polycarbonate dielectric
capacitor
Worst case drift less than
2.5 mV/sec
Sample and Hold
TL/H/7758– 4
High Speed Amplifier with Low Drift and Low Input Current
TL/H/7758– 5
6
Page 7
Typical Applications (Continued)
²
Fast
Summing Amplifier
*In addition to increasing
speed, the LM101A raisesSmall Signal Bandwidth: 3.5 MHz
high and low frequencySlew Rate: 10V/mS
gain, increases output
drive capability and eliminates
thermal feedback.
Connection Diagrams
Metal Can Package
TL/H/7758– 13
*Package is connected to Pin 4 (Vb)
**Unused pin (no internal connection) to allow for input anti-leakage guard
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