Chapter 3. Amplifiers and Signal Processing

Transcription

1 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. Chapter 3. Amplers and Sgnal Pressng 3.1 Ideal OP Amps Op amp Hgh-gan d derental ampler D pwer supples are requred Usually used wth external negatve eedbak Assume deal p amp desgn rut hek nndeal haratersts are mprtant mdy neessary v 1 v 2 V V v 1 d Av v b 2 1 g v 2 Ideal Charatersts A (gan s nnte) 0 when v1 v2 (n set vltage) d (nput mpedane s nnte) 0 (utput mpedane s zer) Bandwdth (n requeny respnse lmtatn) and n phase sht Tw Bas ules ule 1 When the p amp utput s n ts lnear regn, the tw nput termnals are at the same vltage. ule 2 N urrent lws nt ether nput termnal the p amp. Saturatn utput at slghtly lwer than pwer supply vltages 3.2 Invertng Amplers Invertng ampler and nput-utput haraterst 1 Eung Je W

2 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. v v 0 v Vrtual grund: v 0 Analyss: v v r v v and ut 0 n Summng ampler: v F HG v 1 1 v 2 2 I KJ v 2 2 v Nnnvertng Amplers Unty-gan llwer r buer: v v, n, and ut 0 v Nnnvertng ampler and nput-utput haraterst v v Analyss: v v d 1 n and ut Eung Je W

3 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. v 0 v v 3.4 Derental Amplers v v 1 v v 2 v 4 3 v 5 v One-p-amp derental ampler 4 Analyss: v5 v v 4, v v 5 v 4, v 4 v v 3 b 4 3 g Cmmn-mde rejetn rat (CM): CM G r 20lg Gd G Gd Derental mde gan, Gd 4 3 Cmmn mdel gan, G : gan r v3 v4 n (uld be small) and ut 0 Three-p-amp derental ampler (nstrumentatn ampler) Analyss: v v b g, v v F HG, v3v db I b 1 2g, v v KJ 3 Eung Je W

4 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. v F HG I K J 4 v 2 v 1 3 b g Cmmn-mde rejetn rat (CM): CM G r 20lg Gd G Gd Derental mde gan, G d F HG I K J Cmmn mdel gan, G : gan r v n and ut 0 v db 3.5 Cmparatrs Smple mparatr r Shmtt trgger V sat v v re V sat 0 v re v v v v V and v v v V re mnmzes verdrvng p amp nput. Senstve t nse at nput sat re sat v and v re an be nterhanged. Cmparatr wth hysteress Pstve eedbak wth 2 and 3 hysteress nsenstve t nput nse Analyss v Vsat v 3 V sat v must be greater than v re 3 V 2 3 sat 2 3 t prdue v V sat 4 Eung Je W

5 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. v Vsat v 3 V sat v re 3 V 2 3 sat 2 3 t prdue v 3 ntrls the wdth the hysteress. V v must be smaller than sat v v re 1 1 v V sat v V sat v re 3.6 eters x b g 1 x D 2 D 1 v V sat D 4 D 3 v v x 0 v Full-wave presn reter v 0 D2 and D3 ON, D1 and D4 OFF upper p amp rut bemes a nnnvertng ampler wth gan 1 x, lwer p amp rut has n eet n utput 5 Eung Je W

6 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. v 0 D2 and D3 OFF, D1 and D4 ON upper p amp rut has n eet n utput bemes a nnnvertng ampler wth gan 1 x, lwer p amp rut bemes an nvertng ampler wth gan 1 x Varable gan and hgh nput mpedane Hal-wave presn reter Upper r lwer p amp rut 2k 1k v L 3k One p-amp ull-wave reter Gan s a untn lad nstant lad s requred 3.7 Lgarthm Amplers 9 v v V sat 0 1 v 10 Wthut bstng Fr a transstr, V BE F H G IC lg wth reverse saturatn urrent I S I KJ I S A at 27 C Transdde nguratn: I C v and v V F BE lg H G v I S I KJ 6 Eung Je W

7 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. 7 2 Fr 10 A I C 10 A, 0.66 V 0.36 V Wth bstng: same as nnnvertng ampler Temperature mpensatn r auray Antlg (expnental) rut: nterhange resstr wth transstr Applatns Multplatn, dvsn, pwer Dynam range mpressn Lnealzatn 3.8 Integratrs v S 2 C v S 1 Integratr Intal ndtn settng: S 1 pen and S 2 lsed v v (nvertng ampler) and v ( 0) v 1 Integratn: S 1 lsed and S 2 pen v C dt v v and z t 1 v C vdt 1 v 0 Hld: S 1 pen and S 2 pen s hld Frequeny respnse: V j Z ( ) 1 jc 1 1 V ( j) Z jc j Drt and saturatn prblem zt Eung Je W

8 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. 100 I HP 10 BP Fgure 3.10 Bde plt (gan versus requeny) r varus lters. Integratr (I); derentatr (D); lw pass (LP), 1, 2, 3 setn (ple); hgh pass (HP);bandpass (BP). Crner requenes r hgh-pass, lw-pass, and bandpass lters. 1 LP D k Frequeny, Hz Charge ampler Vrtual grund sc s 0 lng able an be used z K dx t 1 1 s v K dx dt C dt dt Kx 0 C Drt and saturatn prblem Large eedbak resstr Prevents saturatn Hghpass lter wth ver vltage ampler 1 2C n requeny respnse mprvement 8 Eung Je W

9 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. s C dq dt K dx dt s Pezeletr sensr s sc s FET 3.9 Derentatrs v C Derentatr C dv and v C dv dt dt Frequeny respnse: V j Z ( ) jc j V ( j) Z 1 jc Derentatr utput: tends t sllate and nsy due t amplatn hgh requeny mpnents 3.10 Atve Flters Lw-Pass Flter 9 Eung Je W

10 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. C v Frequeny respnse: V j Z ( ) V ( j) Z d 1 jc jc 1 j C 1 1 j d b g I 1 r wth 12 C rut bemes nvertng ampler wth gan I 1 r, rut bemes ntegratr Cut requeny r rner requeny: 12 C Hgh-Pass Flter C v Frequeny respnse: V j Z ( ) V ( j) Z jc j 1 jc 1 jc 1 j b g I 1 r wth 12 C, rut bemes derentatr I 1 r, rut bemes nvertng ampler wth gan Cut requeny r rner requeny: 12 C 10 Eung Je W

11 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. Band-Pass Flter C v C Seres mbnatn lwpass and hghpass lter Tw ut requenes r rner requenes: 1 12 C and 2 12 C wth I I 2 1 1, rut bemes derentatr 2, rut bemes ntegratr 3.11 Frequeny espnse Fr a real p amp, bandwdth s nt nnte. Open-Lp Gan Op amp s mult-stage d derental ampler wth hgh gan Stray r juntn apatanes n eah stage gan attenuatn ( 1 slpe n lg-lg plt and 90 phase sht per stage) slpe hanges wth requeny eal p amp has a lmted pen-lp bandwdth Pssble sllatn (gan greater than 1 at 180 phase sht) Cmpensatn Add a apatr (external r nternal) xed slpe 1 and maxmal phase sht 90, pen-lp ut requeny abut 40 Hz N sllatn Clsed-Lp Gan Clsed-lp gan s usually muh smaller than the maxmal pen-lp gan p amp. Clsed-lp gan s determned by external elements rmng negatve eedbak Eung Je W

12 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. Clsed-lp gan an never exeed pen-lp gan. Lp Gan Lp gan = (pen-lp gan p amp) (lsed-lp gan p amp rut) At lw requeny: hgh lp gan, external eedbak rut determnes the p amp rut At hgh requeny: lw lp gan, the p amp rut llws the p amp penlp gan Hgh lp gan hgh auray and stablty Measurement lp gan Break eedbak lp at any pnt n the lp Injet a sgnal Measure the gan arund the lp Examples Unty gan llwer: lp gan = pen-lp gan v v Invertng ampler wth gan 1: lp gan = (pen-lp gan)/2 Gan-Bandwdth Prdut Gan-bandwdth prdut = (gan at ) (bandwdth at ) Unty-gan-bandwdth prdut s gven n speatn p amp Cmpensated p amp has gan slpe 1 Unty - gan - bandwdth prdut n Hz Bandwdth p amp rut = Op amp rut gan Slew ate Fr an p amp, nternal urrent sure has ts I max. Change n vltage arss the mpensatn apatr: dv I max dv s lmted dt C dt 12 Eung Je W

13 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. dv Slew rate Sr dt max Fr snusdal nput, ull-pwer respnse r maxmal requeny r rated utput s Sr p where V r s the rated utput vltage. 2 Vr Unmpensated p amp s aster useul r mparatrs 3.12 Oset Vltage Fr a real p amp, v2 v1 0 t prdue 0. Oset vltage = v v must be nsdered r small nput sgnals Nullng Add an external nullng pt. Adjust the pt nrease I E at ne nput and derease at the ther v2 v1 0 Drt Temperature hange (envrnment r sel-heatng) hange n set vltage, b v v 2 1 g 13 Eung Je W

14 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. Speatn Maxmal set vltage hange per C suh as 0.1 V/C Maxmal set vltage ver a gven temperature range suh as 25 t +85 C Nse Semndutr juntns nse vltage sures and nse urrent sures Fr lw sure mpedane ( 1 and 2 small), v n dmnates. Charatersts andm At lw requeny ampltude 1 (lker nse) At mdrequeny smaller ampltude expressed n rms unts VHz Sme p amps exhbt bursts nse (pprn nse) v n v 1 n v d Av d 2 n v Bas Current Base r gate urrent t keep transstrs turned n bas urrent 0 Bas urrent lws thrugh eedbak resstrs smaller resstrs are desrable (abut 10 k) Cautn: urrent lwng thrugh eedbak resstrs plus urrent lwng thrugh lads must be smaller than p amp utput urrent ratng t small resstrs annt be used Derental Bas Current Derene between tw nput bas urrents << eah bas urrent Cmpensatn resstr mnmzes the eet bas urrents 14 Eung Je W

15 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. v d Drt Change bas urrents due t temperature Cmpensatn resstr als mnmzes the eet bas urrent drt Nse Nse urrents lw thrugh external equvalent resstrs n n d A d + n Fgure 3.14 Nse sures n an p amp The nse-vltage sure v n s n seres wth the nput and annt be redued. The nse added by the nse-urrent sures In an be mnmzed by usng small external resstanes. L NM { b g b g } 2 2 t n n 1 n Ttal rms nse vltage s v v 4kT 4kT BW 1 and 2 : equvalent sure resstanes O QP 12 1 v n : mean value rms nse vltage n VHz 2 ver a requeny range 1 n : mean value rms nse vltage n A Hz 2 ver a requeny range 15 Eung Je W

16 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. k: Bltzmann s nstant T: temperature, K BW: nse bandwdth, Hz Types p amp Small (10 k) sure resstanes BJT nput p amp prdues smaller nse Large sure resstanes FET nput p amp prdues smaller nse due t smaller nse urrent Lw nse a ampler desgn (nnnvertng ampler) by mpedane mathng Charaterst nse resstane s n vn n 12 n 2 Set n 2 usng a transrmer wth turns rat 1:N where N b g 2 1:N v s 3.14 Input and Output esstane Input esstane Op amp derental nput resstane, d : T r FET, M r BJT Ampler-rut nput resstane, a Unty-gan llwer: v Avd Abv vg v a vd v v v A1 d d b g d b A 1g d Ad, a uld be > T a d blp gan v Nnnvertng amplers: leakage urrent v Invertng ampler: a, usually small Av A 1 g, very hgh, lmted by surae 16 Eung Je W

17 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. d v d v Av d v L C L Output esstane Op amp utput resstane, 40 Ampler-rut utput resstane, a r unty-gan llwer wth resstve lad esstve lad, L hange n utput urrent, vd v Avd Av b A1gv v a A, a uld be < A All nnnvertng and nvertng amplers: a d blp gang, very small, lad resstane s lmted by maxmal utput urrent p amp (t small lad resstane p amp saturates nternally) a r unty-gan llwer wth apatve lad Capatve lad, C L C d L dt, lmted by maxmal utput urrent p amp and slew rate CL lwpass lter addtnal phase sht arund the lp pssble sllatn T prevent sllatn, add a small resstr between and C L. Current bster r large utput urrent: p amp + hgh-pwer transstrs 3.15 Phase-Senstve Demdulatrs Cnsder the ampltude-mdulated (AM) sgnal, v () t x()s t t Sgnal: x( t) wth maxmal requeny muh less than Carrer: s t wth 2 AM Eung Je W

18 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. Detetn (r demdulatn) the sgn Envelpe detetn etatn and lwpass lterng Nse at varus requenes annt be rejeted Tuned ampler r bandpass lter an remve sme nse. Phase-senstve demdulatn r synhrnus detetn Multplatn r swthng and lwpass lterng Exellent nse rejetn Phase-senstve demdulatn r xt () s t Assume the llwng, v () t s ts t AM s b g v() t s b Lwpass Flter s rner g yt () v () t s t v() t v ()s t t AM b g 1 m b g r xt ()s t s t xt () s2t s 2 yt () 1 s xt () 2 I b 2 2n 1 g wth n = 0, 1, 2, and s nstant, then we an detet x () t rm v () t x()s t t. AM Nse nt synhrnzed wth v () t s t s rejeted Eung Je W

19 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv Eung Je W

20 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. Cruts: analg multpler, balaned mdulatr/demdulatr, rng demdulatr (a) (b) () (d) 20 Eung Je W

21 Dept. Bmed. Eng. BME302: Bmedal Instrumentatn Kyung Hee Unv. Example (a) xt () s2t 3 b g m b2g 3r b2 30g (b) vam () t s t s t m b g r b g () v 2 () t s2t 3 s 2 30t 1 (e) yt () s2t 3 2 m b g r 3.16 Mrmputers n Medal Instrumentatn Sensrs Analg Sgnal Pressng ADC Mrpressr System DAC I/O - User Interae - DSP - Cntrl - Strage - Cmmunatn - Et Eung Je W