Diodes Waveform shaping Circuits

Transcription

1 des Waefrm shapng Cruts Leture ntes: page 2-2 t 2-31 Sedra & Smth (6 th Ed): Se. 4.5 & 4.6 Sedra & Smth (5 th Ed): Se. 3.5 & 3.6 F. Najmabad, ECE65, Wnter 212

2 Tw-prt netwrks as buldng blks Reall: Transfer funtn f a tw-prt netwrk an be fund by slng ths rut ne. Cnept f nput resstane an be used t fnd / sg (wll be dsussed n transstr amplfer setn)! We fus n fndng transfer funtn, s (rut belw) Open-lp Transfer funtn (R L r ) F. Najmabad, ECE65, Wnter 212

3 Retfer Crut F. Najmabad, ECE65, Wnter 212 L R / Law : KL : KCL : Ω + and de OFF: L R < < < / and de ON : L R and de OFF, Fr and de ON, Fr <

4 Retfer Crut: s the pste prtn Fr Fr <,, de ON de OFF and and F. Najmabad, ECE65, Wnter 212

5 Applatn f Retfer Crut: AC t C nertr fr pwer supply Half-wae retfer (nly nerts half f AC nput t C alue) Full-wae retfer (nerts all f AC nput t C alue) F. Najmabad, ECE65, Wnter 212

6 Eah par f ddes ndut nly fr half f the yle F. Najmabad, ECE65, Wnter 212

7 Clpper r Lmter Crut (pen-lp transfer funtn) F. Najmabad, ECE65, Wnter 212 R < < + ) / ( R and OFF: de < and ON : de < and de OFF, Fr and de ON, Fr

8 Clpper Crut des nt allw > t g thrugh Fr Fr <,, de ON de OFF and and F. Najmabad, ECE65, Wnter 212 Impat f R L s dsussed as an exerse prblem

9 Retfer & lpper ruts are the same but s taken at dfferent latns Half-wae Retfer Clpper F. Najmabad, ECE65, Wnter 212

10 Clpper rut lmts when the dde s ON By adjustng we an adjust lmtng ltage! F. Najmabad, ECE65, Wnter 212

11 Lmtng ltage an be adjusted lmted t + C lmted t + Z F. Najmabad, ECE65, Wnter 212

12 Bttm prtn f sgnal an als be lpped lmted t C lmted Z F. Najmabad, ECE65, Wnter 212

13 Bth tp & bttm prtns f the sgnal an be lpped smultaneusly lmted t + C1 and C2 lmted t + Z1 and Z2 F. Najmabad, ECE65, Wnter 212

14 Ideal Peak etetr Crut Beause annt hange suddenly, the state f dde wll depend nt nly n but als n the hstry f the rut (e.g., d /dt, at ertan tmes,) de OFF: and < Capatr des nt harge r dsharge! (t) where s the apatr ltage at the mment dde turned OFF! nst. < < + F. Najmabad, ECE65, Wnter 212

15 Ideal Peak etetr Crut (pen-lp transfer funtn) de ON : and C d dt C d dt d( ) dt C d dt Fr d Fr /dt < & + : + : de ON de OFF,, nst Beause state f dde depends n, we annt prdue a unersal plt s F. Najmabad, ECE65, Wnter 212

16 Respnse f the Ideal Peak etetr (1) Fr d Fr /dt < & + : + : de ON de OFF,, nst Start at t wth Fr t >, d /dt >. Fr < +, dde remans OFF. When +, dde turns ON (sne d /dt > ) Capatr starts t harge and traks - F. Najmabad, ECE65, Wnter 212

17 Respnse f the Ideal Peak etetr (2) Fr d Fr /dt < & + : + : de ON, de OFF, nst Cap ntnue t harge untl + ( + - ) Afterward starts t derease (d /dt < ) and dde turns OFF. + Een when starts t nrease (d /dt > ) dde remans OFF as < ! de turns ON + and mmedately turns OFF starts t derease (d /dt < ) F. Najmabad, ECE65, Wnter 212

18 Respnse f the Ideal Peak etetr (3) s the peak alue f nput waefrm ( + ): Peak etetr Nte dd nt drp after the peak was dereased n the 3 rd yle. Exerse: Shw that f the dde dretn s reersed, rut detets the negate peak alue, (.e., lwest ltage f the wae frm whh shuld be negate) F. Najmabad, ECE65, Wnter 212

19 Pratal Peak etetr Crut (1) A resstr s added n parallel t the apatr! (It an be the lad fr the rut) de OFF: and < Capatr dsharges nt the resstr wth a tme nstant f τ RC ( t) exp[ - ( t t )/ τ ] < < ( t) + F. Najmabad, ECE65, Wnter 212

20 Pratal Peak etetr Crut (2) F. Najmabad, ECE65, Wnter 212 and ON : de ] )/ ( exp[ ) ( de OFF, : Fr, de ON : &, Fr τ t t - t /dt d + < + ( ) dt d dt d C dt d C dt d C

21 Respnse f the Pratal Peak etetr (1) Fr d /dt Fr < &, + : + : de ON, de OFF, ( t) exp[ - ( t t )/ τ ] Start at t wth Fr t >, d /dt >. Fr < +, dde remans OFF. When +, dde turns ON (sne d /dt > ) Capatr starts t harge and traks - F. Najmabad, ECE65, Wnter 212

22 Respnse f the Pratal Peak etetr (2) Fr d /dt Fr < &, + : + : de ON, de OFF, ( t) exp[ - ( t t )/ τ ] Cap ntnue t harge untl + ( + - ) Afterward starts t derease (d /dt < ) and dde turns OFF. Capatr dsharges: ( t) exp[ - ( t t)/ τ ] Een when starts t nrease (d /dt > ) dde remans OFF as lng as < + de turns ON when + and harges apatr untl + s reahed) F. Najmabad, ECE65, Wnter 212

23 Respnse f the Pratal Peak etetr (3) Shape f utput sgnal depends n the rat f τ/t deal peak detetr: τ/t Gd peak detetr: τ/t >> 1 As τ/t dereases, the rut departs frm a peak detetr. Fr τ/t << 1, apatr dsharges ery fast and rut resembles a retfer rut ereasng τ/t F. Najmabad, ECE65, Wnter 212

24 Peak detetr s used n AM reeers Carrer wae ampltude s mdulated wth the sund data (sund sgnal s the enelp f the arrer wae) T <<τ RC << arrer T sund F. Najmabad, ECE65, Wnter 212

25 Peak-etetr wth a lad A lpper rut wth a lad R L s smlar t the pen-lp lpper wth R R R L Examples f esgn Ches: As a peak detetr (want τ/t ) R s NOT needed and we shuld set C R L t be large (>>T). Peak detetr rut s used t smth ut the utput ltage f a retfer fr the pwer supply rut (Need a large C!). Fr applatns suh as AM reeer when the peak detetr s used as separate the sgnal frm a arrer, R and C shuld be hsen suh that T << τ RC << T and R << R arrer sund L F. Najmabad, ECE65, Wnter 212

26 Clamp Crut Ideal peak detetr: + Clamp rut: + + ( ) s equal t but shfted dwnward by ( + ) If ampltude f ( + ) hanges, the shft wuld hanges and bemes dstrted! F. Najmabad, ECE65, Wnter 212

27 Clamp Crut wth a Lad Capatr harges when the dde s ON: + Capatr remans harged when dde s OFF. Capatr harges when the dde s ON: + Capatr dsharges nt R L when dde s OFF. As lng as τ R L C >> T apatr dsharges lttle and lamp ruts wrks fne! F. Najmabad, ECE65, Wnter 212

28 ltage shft n a lamp rut an be adjusted! A C + : peak f + A : peak f A + A + C Peak detetr rut: + A + C + C + ( ) C s equal t but shfted dwnward by ( + C ) F. Najmabad, ECE65, Wnter ( ) Z

29 Clamp rut an als ntrdue a pste shft Peak detetr (dde s reersed): ( ) Clamp rut (dde reersed): ( ) + ( ) s equal t but shfted upward by ( ) F. Najmabad, ECE65, Wnter 212

30 The pste shft an als be adjusted. + ( ) C + ( ) Z Hw t fnd respnse f lpper r lamp ruts: Assume dde s ON and alulate. If +, replae wth + (peak pste alue) If, replae wth (peak negate alue) If lpper,. If Clamp, use KL t fnd (e.g.,, ) F. Najmabad, ECE65, Wnter 212