LM108A LM208A LM308A Operational Amplifiers
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
The devices operate with supply voltages from
g
2V to
g
18V 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 LM108A series makes possible
many designs that are not practical with conventional ampli-
fiers In fact it operates from 10 MX source resistances
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
LM208A has its performance guaranteed over a
b
25 C to
a
85 C temperature range instead of
b
55 C to
a
125 C
The LM308A devices have slightly-relaxed specifications
and performances over a 0 C to
a
70 C temperature range
Features
Y
Y
Y
Y
Y
Offset voltage guaranteed less than 0 5 mV
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
Guaranteed 5
mV
C drift
Compensation Circuits
Standard Compensation Circuit
Alternate Frequency Compensation
C
f
t
R1 C
O
R1
a
R2
C
O
e
30 pF
TL H 7759 鈥?1
Improves rejection of power supply
noise by a factor of ten
TL H 7759 鈥?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 鈥?3
C
1995 National Semiconductor Corporation
TL H 7759
RRD-B30M115 Printed in U S A
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