The LM221 series are precision preamplifiers designed to operate with general purpose operational amplifiers to drastically decrease dc errors Drift bias current common 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 mA to 200 mA 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