LM221H Datasheet | National Semiconductor

Description The LM221 series are precision preamplifiers designed to operate with general purpose operational amplifiers to drastically decrease dc errors Drift bias current mon mode and supply rejection are more than a factor of 50 better than standard op amps alone Further the added dc gain of the LM221 decreases the closed loop gain error The LM221 series operates with supply voltages from g 3V to g 20V and has sufficient supply rejection to operate from unregulated supplies The operating current is programmable from 5 m A to 200 m A so bias current offset current gain and noise can be optimized for the particular application while still realizing very low drift Super-gain transistors are used for the input stage so input error currents are lower than conventional amplifiers at the same operating current Further the initial offset voltage is easily nulled to zero The extremely low drift of the LM221 will improve accuracy on almost any precision dc circuit For example instrumentation amplifier strain gauge amplifiers and thermocouple amplifiers now using chopper amplifiers can be made with the LM221 The full differential input and high monmode rejection are another advantage over choppers For applications where low bias current is more important than drift the operating current can be reduced to low values High operating currents can be used for low voltage noise with low source resistance The programmable operating current of the LM221 allows tailoring the input characteristics to match those of specialized op amps The LM221 is specified over a b25 C to a 85 C range and the LM321 over a 0 C to a 70 C temperature range Features Y Y Y Y Y Y Y Guaranteed drift of LM321A 0 2 m V C Guaranteed drift of LM221 series 1 m V C Offset voltage less than 0 4 m V Bias current less than 10 n A at 10 m A operating current CMRR 126 d B minimum 120 d B supply rejection Easily nulled offset voltage Typical Applications Thermocouple Amplifier with Cold Junction pensation Set for 2 98V...