Operational Amplifiers
Description
LM108A LM208A LM308A Operational Amplifiers
May 1989
LM108A LM208A LM308A Operational Amplifiers
General Description
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 g 2V to g 18V 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 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
Cf t
R1 CO R1 a R2
CO e 30 pF
TL H 7759 – 1
Improves rejection of power supply noise by a factor of ten
TL H 7759 – 2
Bandwidth and slew rate are ...
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