LM321 ,Precision Preamplifierapplications where low bias current is more important thanandsupplyrejectionaremorethanafactorof50b ..
LM3211MTADJ ,Step-up PWM DC/DC Converter Integrated with 4 BuffersApplicationsLM3211 uses a patented internal circuitry to limit startupinrush current of the boost s ..
LM3211MT-ADJ ,Step-up PWM DC/DC Converter Integrated with 4 BuffersApplicationsapplication.The LM3211 contains 4 Gamma buffers capablen Cellular Phones/Digital Camera ..
LM3211MTX-ADJ ,Step-up PWM DC/DC Converter Integrated with 4 BuffersFeaturesn 1.4A, 0.17Ω, internal power switchThe LM3211 is a compact bias solution for TFT displays. ..
LM321H ,LM221/LM321 Precision Preamplifiers
LM321MF ,Low Power Single Op AmpElectrical Characteristics Unless otherwise specified, all limits guaranteed for at T = 25˚C; V = 5 ..
LMC6064AIMX ,Precision CMOS Quad Micropower Operational AmplifierElectrical Characteristics+ −Unless otherwise specified, all limits guaranteed for T = 25˚C. Boldfa ..
LMC6064AIN ,Precision CMOS Quad Micropower Operational AmplifierFeaturesThe LMC6064 is a precision quad low offset voltage, mi- (Typical Unless Otherwise Noted)cro ..
LMC6064IM ,Precision CMOS Quad Micropower Operational Amplifierfeatures, plus its low power consump-n Output swing within 10 mV of supply rail, 100k loadtion make ..
LMC6064IMX ,Precision CMOS Quad Micropower Operational Amplifierfeatures,see the LMC6061 or LMC6062 respectively. n Medical instrumentationn D/A converterPATENT PE ..
LMC6064IN ,Precision CMOS Quad Micropower Operational Amplifierapplications using the LMC6064 include precisionn Improved latchup immunityfull-wave rectifiers, in ..
LMC6081 ,Precision CMOS Single Operational Amplifierfeatures,bYInput common-mode range includes Vplus its low offset voltage, make the LMC6081 ideally ..
LM321
Precision Preamplifier
TL/H/7769
LM221/LM321
Precision
Preamplifiers
February 1995
LM221/LM321 Precision Preamplifiers
General Description
The LM221 seriesare precision preamplifiers designedto
operate with general purpose operational amplifiersto dras-
tically decreasedc errors. Drift,bias current, common mode
and supplyrejectionare morethana factorof50 better than
standardop amps alone. Further,the addeddc gainofthe
LM221 decreasesthe closed loop gain error.
The LM221 series operates with supply voltages from g3V g20Vandhas sufficient supply rejectionto operate from
unregulated supplies.The operating currentis programma-
blefrom5 mAto200mAso bias current, offset current, gain
and noise canbe optimizedforthe particular application
whilestill realizing verylow drift. Super-gain transistorsare
usedforthe input stageso input error currentsare lower
than conventional amplifiersatthe same operating current.
Further,the initial offset voltageis easily nulledto zero.
The extremelylowdriftofthe LM221will improve accuracy almostany precisiondc circuit.For example, instrumen-
tation amplifier, strain gauge amplifiersand thermocouple
amplifiers now using chopper amplifierscanbe made with
the LM221. Thefull differential input and high common-
mode rejectionare another advantage over choppers.For
applications wherelow bias currentis more important than
drift,the operating current canbe reducedtolow values.
High operating currentscanbe usedforlow voltage noise
withlow source resistance. The programmable operating
currentofthe LM221 allows tailoringthe input characteris-
ticsto match thoseof specializedop amps.
The LM221is specified overa b25§Cto a85§C rangeand
the LM321 overa 0§Cto a70§C temperature range.
Features Guaranteed driftof LM321AÐ0.2 mV/§C Guaranteed driftof LM221 seriesÐ1 mV/§C Offset voltage less than0.4mV Bias current less than10nAat10mA operating current CMRR126dB minimum 120dB supply rejection Easily nulled offset voltage
Typical Applications
ThermocoupleAmplifierwith ColdJunction Compensation
TL/H/7769–1
*Setfor 2.98Vat outputwith LM113
shorted. Output should equal ambi-
ent temperatureat10 mV/§K.
²Adjustfor output readingin§C.
C1995National SemiconductorCorporation RRD-B30M115/PrintedinU.S.A.
