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參數(shù)資料
| 型號(hào)： | LF257 |
| 廠商： | 意法半導(dǎo)體 |
| 英文描述： | Wide Bandwidth Single J-FET Operational Amplifiers(寬帶J-FET單運(yùn)放) |
| 中文描述： | 寬帶單的J - FET的運(yùn)算放大器（寬帶的J - FET的單運(yùn)放） |
| 文件頁(yè)數(shù)： | 5/14頁(yè) |
| 文件大?。?/td> | 249K |
| 代理商： | LF257 |
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TheLF155,LF156,LF157series areopampswithJ-
FETinputtransistors.TheseJFETshavelargereverse
breakdownvoltagesfromgatetosourceor drainelimi-
natingtheneedofclampsacrosstheinputs.Therefore
large differentialinput voltagescan easily beaccom-
modatedwithoutalargeincreaseofinputcurrents.The
maximum differential input voltage is independentof
thesupplyvoltage.However,neitherofthenegativein-
putvoltagesshouldbe allowedto exceedthenegative
supplyas this will cause large currentsto flowwhich
canresultin adestroyedunit.Exceedingthenegative
common-modelimit oneitherinputwillcauseareversal
of thephasetotheoutputandforcethe amplifieroutput
to the correspondinghigh or lowstate. Exceedingthe
negativecommon-modelimit on bothinputs will force
theamplifieroutputtoahighstate.Inneithercasedoes
a latch occur since raising the input back within the
common-moderangeagainputstheinputstageand
thustheamplifierinanormaloperatingmode.Exceed-
ingthepositivecommon-modelimitonasingleinputwill
notchangethephaseoftheoutputhowever,ifbothin-
putsexceedthelimit, theoutputof theamplifier will be
forcedtoahighstate.Theseamplifierswill operatewith
thecommon-modeinputvoltageequaltothe positive
supply. In fact, the common-modevoltagecanex-
ceedthepositivesupplybyapproximately100mVinde-
pendentof supply volt-age and over thefull operat-
ingtemperaturerange.The positive suplly can there-
forebeusedasareferenceonaninputas,forexample,
inasupplycurrentmonitorand/orlimiter. Precautions-
shouldbetakentoensurethatthepowersupplyforthe
integratedcircuitneverbecomesre-versedinpolarity
orthattheunitisnotinadvertentlyin-stalledbackwards
ina socket as an unilimited currentsurge throughthe
resultingforwarddiodewithin theIC couldcausefusin-
goftheinternalconductorsandresultinadestroyedunit.
Becausetheseamplifiers areJFETratherthanMOS-
FET input op amps they do not require special han-
dling.
AllofthebiascurrentsintheseamplifiersaresetbyFET
currentsources. The drain currents for the amplifiers
are therefore essentially independent of supply volt-
ages.
Aswith mostamplifiers,careshouldbetakenwithlead
dress,componentsplacementandsupplydecoupling
inordertoensurestability.Forexample,resistorsfrom
theoutputtoan inputshouldbe placedwith thebody
closetotheinputtominimiz”pickup”andmaximize the
frequencyof the feedbackpoleby minimizing theca-
pacitancefromtheinput toground.
A feedbackpoleis createdwhenthe feedbackaround
anyamplifier is resistive. The parallel resistance and
capacitancefromtheinput of thedevice(usuallythe in-
vertinginput)toacgroundsetthefrequencyofthepole.In
many instances the frequency of this pole is much
greaterthantheexpected3dBfrequencyof the closed
loopgainandconsequentlythereisnegligibleeffecton
stabilitymargin. However, if thefeedbackpoleis less
than approximately six time the expected 3 dB fre-
quencyaleadcapacitorshouldbeplacedfromtheout-
puttotheinputoftheopamp.Thevalueofthatadded
capacitorshouldbesuchthattheRC timeconstantof
thiscapacitorandtheresistanceitparallels isgreater
thanor equal to theoriginal feedbackpoletime con-
stant.
APPLICATION HINTS
LF155 - LF156 - LF157
5/14
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PDF描述 |
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| LF33CPT | VERY LOW DROP VOLTAGE REGULATORS WITH INHIBIT |
| LF33ABDT-TR | VERY LOW DROP VOLTAGE REGULATORS WITH INHIBIT |
| LF12ABV5V | GT 25C 25#16 SKT RECP WALL RM |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LF257D | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:WIDE BANDWIDTH SINGLE J-FET OPERATIONAL AMPLIFIERS |
| LF257H | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Series Monolithic JFET Input Operational Amplifiers |
| LF257M | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Voltage-Feedback Operational Amplifier |
| LF257N | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:WIDE BANDWIDTH SINGLE J-FET OPERATIONAL AMPLIFIERS |
| LF25AB | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Very low drop voltage regulators with inhibit |
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