LM208 [NSC]
Operational Amplifiers; 运算放大器
| 型号： | LM208 |
| 厂家： | 
National Semiconductor |
| 描述： | Operational Amplifiers |
| 文件： | 总8页 (文件大小：160K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
May 1989
LM108A/LM208A/LM308A Operational Amplifiers
General Description
The LM108/LM108A series are precision operational ampli-
fiers 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 ad-
justments, in most cases, and obtain performance ap-
proaching chopper stabilized amplifiers.
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 us-
ing capacitors no larger than 1 mF.
The LM208A is identical to the LM108A, except that the
b
LM208A has its performance guaranteed over a 25 C to
§
85 C temperature range, instead of 55 C to 125 C.
a
b
a
The LM308A devices have slightly-relaxed specifications
§
§
§
g
18V and have sufficient supply rejection to use unregulat-
The devices operate with supply voltages from
g
2V to
a
and performances over a 0 C to 70 C temperature range.
§
§
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.
Features
Y
Offset voltage guaranteed less than 0.5 mV
Y
Y
Y
Y
Maximum input bias current of 3.0 nA over temperature
Offset current less than 400 pA over temperature
Supply current of only 300 mA, even in saturation
The low current error of the LM108A series makes possible
many designs that are not practical with conventional ampli-
fiers. In fact, it operates from 10 MX source resistances,
Guaranteed 5 mV/ C drift
§
Compensation Circuits
Standard Compensation Circuit
Alternate* Frequency Compensation
R1 C
O
a
R1 R2
*Improve
noise b
30 pF
TL/H/7759–1
.
TL/H/7759–2
**Bandwidth and slew rate are proportional to 1/C
f
**Bandwidth and slew rate are proportional to 1/C
.
s
Feedforward Compensation
TL/H/7759–3
C
1995 National Semiconductor Corporation
TL/H/7759
RRD-B30M115/Printed in U. S. A.
LM108A/LM208A Absolute Maximum Ratings
b
a
65 C to 150 C
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
(Note 5)
Storage Temperature Range
§
§
Lead Temperature (Soldering, 10 sec.) (DIP)
260 C
§
Soldering Information
Dual-In-Line Package
Soldering (10 sec.)
g
Supply Voltage
20V
260 C
§
Power Dissipation (Note 1)
Differential Input Current (Note 2)
Input Voltage (Note 3)
500 mW
Small Outline Package
Vapor Phase (60 sec.)
Infrared (15 sec.)
215 C
§
g
10 mA
220 C
§
g
15V
Continuous
See An-450 ‘‘Surface Mounting Methods and Their Effect
on Product Reliability’’ for other methods of soldering sur-
face mount devices.
Output Short-Circuit Duration
Operating Free Air Temperature Range
LM108A
LM208A
b
b
a
55 C to 125 C
§
25 C to 85 C
§
§
ESD Tolerance (Note 6)
2000V
a
§
Electrical Characteristics (Note 4)
Parameter
Conditions
Min
Typ
0.3
0.05
0.8
70
Max
0.5
Units
mV
nA
e
e
e
e
e
Input Offset Voltage
Input Offset Current
Input Bias Current
Input Resistance
T
T
T
T
T
T
25 C
§
A
A
A
A
A
A
25 C
§
0.2
25 C
§
2.0
nA
25 C
§
30
80
MX
mA
Supply Current
25 C
§
0.3
0.6
e
e
g
Large Signal Voltage Gain
25 C, V
§
15V,
S
300
1.0
V/mV
mV
t
10 kX
e
g
V
10V, R
OUT
L
Input Offset Voltage
1.0
5.0
0.4
2.5
Average Temperature Coefficient
of Input Offset Voltage
mV/ C
§
Input Offset Current
nA
Average Temperature Coefficient
of Input Offset Current
0.5
pA/ C
§
Input Bias Current
Supply Current
3.0
0.4
nA
e
T
A
125 C
§
0.15
mA
e
t
e
g
g
Large Signal Voltage Gain
V
15V, V
10V,
S
OUT
40
V/mV
R
10 kX
L
S
S
e
e
e
g
g
g
g
14
Output Voltage Swing
V
V
15V, R
10 kX
13
V
V
L
g
Input Voltage Range
15V
13.5
96
Common Mode Rejection Ratio
Supply Voltage Rejection Ratio
110
110
dB
dB
96
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.
g
Note 3: For supply voltages less than 15V, the absolute maximum input voltage is equal to the supply voltage.
s
s
s
s
125 C, unless otherwise specified. With the LM208A, however, all temperature
A
b
g
g
20V and 55 C
Note 4: These specifications apply for 5V
s
V
T
§
§
S
s
85 C.
b
specifications are limited to 25 C
T
§
§
A
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.
Lead Temperature (Soldering, 10 sec.) (DIP)
260 C
§
Soldering Information
Dual-In-Line Package
Soldering (10 sec.)
Small Outline Package
Vapor phase (60 sec.)
Infrared (15 sec.)
g
Supply Voltage
18V
260 C
§
Power Dissipation (Note 1)
Differential Input Current (Note 2)
Input Voltage (Note 3)
500 mW
215 C
§
g
10 mA
220 C
§
g
15V
Continuous
See An-450 ‘‘Surface Mounting Methods and Their Effect
on Product Reliability’’ for other methods of soldering sur-
face mount devices.
Output Short-Circuit Duration
Operating Temperature Range
Storage Temperature Range
a
0 C to 70 C
§
65 C to 150 C
§
§
b
a
ESD rating to be determined.
§
H-Package Lead Temperature
(Soldering, 10 sec.)
300 C
§
Electrical Characteristics (Note 4)
Parameter
Conditions
Min
Typ
0.3
0.2
1.5
40
Max
0.5
1
Units
mV
nA
e
e
e
e
e
Input Offset Voltage
Input Offset Current
Input Bias Current
Input Resistance
T
T
T
T
T
T
25 C
§
A
A
A
A
A
A
25 C
§
25 C
§
7
nA
25 C
§
10
80
MX
mA
e
e
g
g
Supply Current
25 C, V
§
15V
0.3
0.8
S
e
Large Signal Voltage Gain
25 C, V
15V,
§
S
300
2.0
2.0
V/mV
mV
t
10 kX
e
g
g
g
V
V
V
10V, R
OUT
L
e
e
e
Input Offset Voltage
15V, R
100X
100X
0.73
5.0
1.5
10
S
S
S
e
Average Temperature Coefficient
of Input Offset Voltage
15V, R
S
mV/ C
§
Input Offset Current
nA
Average Temperature Coefficient
of Input Offset Current
pA/ C
§
Input Bias Current
10
nA
e
e
g
g
Large Signal Voltage Gain
V
15V, V
10V,
S
OUT
60
V/mV
t
e
e
R
10 kX
L
S
S
e
g
g
g
g
g
14
Output Voltage Swing
V
V
15V, R
10 kX
13
14
V
V
L
Input Voltage Range
15V
Common Mode Rejection Ratio
Supply Voltage Rejection Ratio
96
96
110
110
dB
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.
g
Note 3: For supply voltages less than 15V, the absolute maximum input voltage is equal to the supply voltage.
s
s
s
s
a
T
A
g
Note 4: These specifications apply for 5V
g
15V and 0 C
V
S
70 C, unless otherwise specified.
§
§
3
Typical Applications
Sample and Hold
²
Teflon, polyethylene or polycarbo
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 pre-
dicted.
Resistors can cause other errors besides gradient generat-
ed 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. Re-
ferred to input, this is a 50 mV error. All of the gain fixing
resistor should be the same material.
Thermocouple effects caused by temperature gradient
across dissimilar metals are perhaps the worst offenders.
Only a few degrees gradient can cause hundreds of micro-
volts of error. The two places this shows up, generally, are
the package-to-printed circuit board interface and tempera-
ture gradients across resistors. Keeping package leads
short and the two input leads close together helps greatly.
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, thermo-
probe, 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
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 er-
rors. Wirewound resistors of evanohm or manganin are best
can be 50 C or more. The device under test along with the
§
gain setting resistor should be isothermal.
since they only generate about 2 mV/ C referenced to cop-
§
per. Of course, keeping the resistor ends at the same tem-
perature is important. Generally, shielding a low drift stage
electrically and thermally will yield good results.
Schematic Diagram
TL/H/7759–6
5
Connection Diagrams
Metal Can Package
Dual-In-Line Package
TL/H/7759–7
Pin 4 is connected to the case.
TL/H/7759–8
Top View
**Unused pin (no internal connection) to allow for input anti-leakage guard
ring on printed circuit board layout.
Order Number LM108AJ-8, LM208AJ-8, LM308AJ-8,
LM308AM or LM308AN
See NS Package Number J08A, M08A or N08E
Order Number LM108AH, LM208AH or LM208AH
See NS Package Number H08C
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
Physical Dimensions inches (millimeters) (Continued)
Molded Dual-In-Line Package (N)
Order Number LM308AN
NS Package Number N08E
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