数字式音量控制电路

141Vol.14No.1()JournalofChongqingTeachersCollege(NaturalScienceEdition)19973Mar.1997X(,,630047)öDAC083274LS193555,256,,,,TN7021DAC0832DöA,DAC0832CMOS8DöA,20,1[1,2],28=256DAC0832:VOUT=VREFRREFR0D721+D622+D523+D424+D325+D226+D127+D028,D0D710,VREF,RREFR0,VOUTD0D7ViVREF,VOUTVi,D0D7,256,274LS19374LS1934,CPUCPD,,CPU;,CPDQCCQCB,NCr,Cr=0,1,2[3,4]X19962052221DAC0832274LS193174LS193CPUCPDCrLDABCDQAQBQCQD5515555500005500ABCDABCD10155551015555110155553555555,555,,,3(a)(b)[5,6]555,5555k8(555)A1A2R2ST2T1:623VCC,A123VCC,A1;A2,213VCC,A2,R2S,Q{,5553,T1,6,,22,13VCC,A2,R2S,3;,T1,623VCC2()14355544,AN2,,,,AN2,,,AN1,,,,AN1,48:NE555(IC4),,20ms(4),AN1AN2IC24574LS193(IC2IC3)8,AN2,,,DAC0832(IC1),IC1,,AN2,IC25,,AN1,,DAC0832,DAC0832DAC0832,LM081,,,Vi10V,DAC08328DöA,,256,31:454,555(),:T=(R1+2R2)C2ln2,[5],R1R2C2,AN1AN2,5s,R1R2C2(256),1012DöADAC0832,74LS193,1,11:,1992.132137(35)4()14AStudyofthePreparationofModifiedFiberandtheRemovalofItsCopperIonsJiaYun(ChongqingInstituteofIronandSteelTechnology,Chongqing,630050)AbstractInthispaper,thepreparationoffiberwithstrawasitsmajormaterialwasex2plored.OnewayofionexchangerandtheremovalconditionandabsorptioncapacityofheavymetalionsCu2+wereobtained.Theresultsshowthatthepreparationofthismodi2fiedfiberhasastrongabsorbabilityofCu2+,whenthevalueofpHisequaltoorgreaterthan6,theabsorptioncapacityofCu2+is10.59mgöL,whileitcanbeelutriatedandreproducedbymeansof5percentofliquidam2moniasolution.Keywordsabsorbent,synthetictest,copperions,modifiedfiber-------------------(4)21()1:182133821353,,11:,1995.70714,11:,1991.808251(3)1:,1990.3653746,15551:,1989.130Digital2controlledVolumeCircuitTangMin(Dept.ofPhysicsandInformationTechnology,ChongqingTeachersCollege,Chongqing,630047)AbstractInthispaper,adigital2controlledvolumecircuitthatcontainsDAC0832,74LS193and555timerisdesignedsuccessfully.Itscontrolledgradeachieves256anditsexternalcircuitisverysimple.Keywordsvolume,circuit,digitalsignal,analogsignal531: