The LM108/LM108A series are precision operational amplifiers
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 adjustments,
in most cases, and obtain performance approaching
chopper stabilized amplifiers.
The devices operate with supply voltages from g2V to
g18V 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 LM108A series makes possible
many designs that are not practical with conventional amplifiers.
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 using
capacitors no larger than 1 mF.
The LM208A is identical to the LM108A, except that the
LM208A has its performance guaranteed over a b25§C to
a85§C temperature range, instead of b55§C to a125§C.
The LM308A devices have slightly-relaxed specifications
and performances over a 0§C to a70§C temperature range.
Features
Y Offset voltage guaranteed less than 0.5 mV
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 5 mV/§C drift