P r o d u c t I n n o v a t i o n F r o m

PA91



PA91U

INPUTPROTECTION

AlthoughthePA91canwithstanddifferentialvoltagesupto±20V,

additional external protection is recommended. Low leakage, low

capacitance JFETs connected as diodes are recommended (e.g.

2N4416, Q1-Q4 in Figure 2).The differential input voltage will be

clampedto±1.4V.Thisissufficientoverdrivetoproducemaximum

powerbandwidth.

POWERSUPPLYPROTECTION

Unidirectionalzenerdiodetransientsuppressorsarerecommended

asprotectiononthesupplypins.SeeFigure2.Thezenersclamp

transientstovoltageswithinthepowersupplyratingandalsoclamp

powersupplyreversalstoground.Whetherthezenersareusedor

not,thesystempowersupplyshouldbeevaluatedfortransientper-

formanceincludingpower-onovershootandpower-offpolarityreversalsaswellaslineregulation.

Conditionswhichcancauseopencircuitsorpolarityreversalsoneitherpowersupplyrailshouldbeavoidedorpro-

tectedagainst.Reversalsoropensonthenegativesupplyrailisknowntoinduceinputstagefailure.Unidirectional

transzorbspreventthis,anditisdesirablethattheybebothelectricallyandphysicallyasclosetotheamplifieras

possible.

STAbILITY

ThePA91isexternallycompensatedandperformancecanbetailoredtotheapplication.Usethegraphsofsmall

signalresponseandpowerresponseasaguide.ThecompensationcapacitorCCmustberatedat500Vworking

voltage.AnNPOcapacitorisrecommended.ThecompensationnetworkCCRCmustbemountedcloselytothe

amplifierpins4and5toavoidspuriousoscillation.

QUIESCENTCURRENTREDUCTION

Whenpin3(IQ)isshortedtopin5(CC2)theABbiasingoftheoutputstageisdisabled.Thisraisesdistortionsince

theoutputstageisthenclassCbiased,butreducesthequiescentcurrentby1mAforapowerdissipationsavings

of0.4W.Pin3maybeleftopenifnotused.

CONTACTINGCIRRUSLOGICSUPPORT

ForallApexPrecisionPowerproductquestionsandinquiries,calltollfree800-546-2739inNorthAmerica.

Forinquiriesviaemail,pleasecontacttucson.support@cirrus.com.

InternationalcustomerscanalsorequestsupportbycontactingtheirlocalCirrusLogicSalesRepresentative.

Tofindtheonenearesttoyou,gotowww.cirrus.com

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