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參數(shù)資料
| 型號： | LF255 |
| 廠商： | 意法半導體 |
| 英文描述： | WIDE BANDWIDTH SINGLE J-FET OPERATIONAL AMPLIFIERS |
| 中文描述： | 寬帶單J - FET的運算放大器 |
| 文件頁數(shù)： | 5/14頁 |
| 文件大?。?/td> | 250K |
| 代理商： | LF255 |
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
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LF255D | WIDE BANDWIDTH SINGLE J-FET OPERATIONAL AMPLIFIERS |
| LF257 | Wide Bandwidth Single J-FET Operational Amplifiers(寬帶J-FET單運放) |
| LF356 | Wide Bandwidth Single J-FET Operational Amplifiers(寬帶J-FET單運放) |
| LF33CPT | VERY LOW DROP VOLTAGE REGULATORS WITH INHIBIT |
| LF33ABDT-TR | VERY LOW DROP VOLTAGE REGULATORS WITH INHIBIT |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LF255D | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:WIDE BANDWIDTH SINGLE J-FET OPERATIONAL AMPLIFIERS |
| LF255H | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Series Monolithic JFET Input Operational Amplifiers |
| LF255M | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Voltage-Feedback Operational Amplifier |
| LF255N | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:WIDE BANDWIDTH SINGLE J-FET OPERATIONAL AMPLIFIERS |
| LF256 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Series Monolithic JFET Input Operational Amplifiers |
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