ECEN474/704: (Analog) VLSI Circuit Design Spring 2018

Transcription

1 ECEN474/704: (Aal) S Cicuit es Sp 08 ectue 9: iffeetial Aplifies Sa Pale Aal & Mixed-Sal Cete Texas A&M Uiesity

2 Auceets & Aeda H ue Ma 6 ead azai Chapte 4 Sle-eded ad diffeetial sals iffeetial pai iffeetial aplifies

3 Sle-Eded & iffeetial Sals A sle-eded sal is easued with espect t a fixed ptetial (ud) A diffeetial sal is easued betwee tw equal ad ppsite sals which sw aud a fixed ptetial (c-de leel) Yu ca decpse diffeetial sals t a diffeetial de (diffeece) ad a c-de (aeae Sle-Eded Sal iffeetial Sal M ut ut CM ut ut

4 Sle-Eded & iffeetial Aplifies iffeetial sal adataes C-de ise ejecti Hihe (ideally duble) ptetial utput sw Siple bias ped leaity Ma disadatae is aea, which is uhly duble Althuh, t et the sae peface sle-eded dess, we fte hae t cease the aea daatically Max Output Sw Max Output Sw GS T GS T 4

5 C-Mde eel Sesitiity A des which uses tw sle-eded aplifies t ealize a diffeetial aplifie is ey sesitie t the c-de put leel The tasists bias cuet ad tascductace ca ay daatically with the c-de put pacts sall-sal a Chaes the utput c-de, which ipacts the axiu utput sw 5

6 iffeetial Pai A M ut ut whee ad O, CM A iped diffeetial aplifie tply utilizes a tail cuet suce t keep the tasist bias cuet ideally cstat e the c-de put ae Allws f a cstat sall-sal a ad utput cde leel Nte, yu still hae t hae keep the put pai ad tail cuet suce tasists satuati 6

7 iffeetial Pai put-output Chaacteistics F lae-sal diffeetial puts, the axiu utput leels ae well defed ad ideally depedet f the put c-de F sall-sal diffeetial puts, the sall-sal a is axiu at lw-put sal leels As the diffeetial put leel ceases, the cicuit beces e lea ad the a deceases 7

8 iffeetial Pai - Chaacteistics (ae Sal) Objectie: Fd the diffeetial tasist cuet ( - ) as a fucti f the put diffeetial ltae ( - ) put ltae iffeece : C Squa bth sides ad us 4 GS Squa bth sides ad us C C GS C GS T ss GS T *Nte, this equati is ly alid f a ceta axiu put diffeetial ltae ( - ) 4 C C C 4 ss 4 C 8

9 iffeetial Pai - Chaacteistics (ae Sal) C ss 4 C C ss The diffeetial cuet is a dd fucti f the diffeetial put ltae which ceases lealy f sall puts F lae diffeetial put ltaes, the utput diffeetial cuet cpesses due t the sqt te The diffeetial utput cuet axes ut whe all the cuet flws thuh e tasist at 9

10 iffeetial Pai - Chaacteistics (ae Sal) F the axiu cuet ae cside the case whe all cuet flws thuh M 0 F 0, ideally GS T GS GS GS T At this, M ust suppt all f Maxiu iffeetial put : GS e ca elate this t the ze diffeetial put edie T C Ze iffeetial put Oedie : GS T, C The diffeetial utput cuet will satuate if the diffeetial put ltae exceeds sqt() ties the equilibiu put edie ltae 0

11 iffeetial Pai Tascductace efe C ss ad C 4 G C The sall - sal 4 ss C 4 ss C tascductace at 0 is G C Cside the lad esists ss, the sall - sal a is A G C ss The diffeetial pai tascductace ad a is axiu ea ze put diffeetial ltae

12 iffeetial Pai Sall-Sal Aalysis Methd - Supepsiti The X utput f is deled as a deeeated CS aplifie Fd ut ( ) ad that Nte X

13 iffeetial Pai Sall-Sal Aalysis Methd - Supepsiti The Y utput f is deled as a Thee equialet di a CG aplifie Fd ut ( ) ad that Nte Y T

14 iffeetial Pai Sall-Sal Aalysis Methd - Supepsiti 4 tt Y X Y X ut ut ut Y X ut ut Ga : iffeetial F the cicuit syety, ttal T fd the

15 iffeetial Pai Sall-Sal Aalysis Methd Half Cicuit The syetic diffeetial pai ca be deled as a Thee equialet t bsee hw the tail de P chaes with the diffeetial put sal f T = T ad the put is a tuly diffeetial sal, de P eas cstat This allws the tail de t be teated as a itual ud 5

16 itual GN Pf F sall sals F diffeetial peati. K aud the put etwks. KC at de P 0 which iplies that P P, ad us the abe K 0 6

17 iffeetial Pai Sall-Sal Aalysis Methd Half Cicuit Apply the itual ud ccept allws del as tw half cicuits X Y iffeetial Ga : X Y 7

18 iffeetial Pai C-Mde espse deally, a diffeetial aplifie cpletely ejects c-de sals, i.e. A,CM =0 eality, the fite tail cuet suce ipedace esults a fite c-de a A, CM ut, CM 8

19 iffeetial Pai with ide ads hile the a f this aplifie is elatiely sall, it is sewhat pedictable, as it is defed by the ati f the tasist sizes ad the /p bility 9 0 Assu C C C C A A p p

20 iffeetial Pai w/ Cuet-Suce ads Assu 0 A hile the a f this aplifie is hihe, it is sewhat upedictable, as it is defed by the tasist utput esistace, which chaes daatically with pcess aiatis 0

21 iffeetial Pai w/ ide & Paallel Cuet-Suce ads Add a paallel cuet suce t a dide cected lad allws f cease a which is still sewhat pedictable the cuet pecetae that the cuet suce "steals" f the dide lad is whee 0 Assu 5 p C C A A

22 Cascde iffeetial Pai Assu A A Us a cascde diffeetial pai ad cascde cuetsuce lads allws f a csideable cease a Hwee, a elatiely lae pwe supply ay be equied t supply the ecessay ltae head t keep all the tasists satuati

23 Next Tie Siple OTA