LM108 LM208 LM308 Operational Amplifiers
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 C to
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 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 LM108 is guaranteed from
b
55 C to
a
125 C the
LM208 from
b
25 C to
a
85 C and the LM308 from 0 C to
a
70 C
Features
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
Guaranteed drift characteristics
Compensation Circuits
Standard Compensation Circuit
Alternate Frequency Compensation
C
f
t
R1 C
O
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
NSC [ NATIONAL SEMICONDUCTOR ]
