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high gain bandwidth product precision fast fet ? op amp AD8067 features ? fe t input ampl ifier : 0. 6 pa inp u t bias curr en t ? s t able f o r gains 8 ? high speed ? 54 mhz, C3 db bandwidth ( g = +1 0) ? 640 v/s sle w ra t e ? l o w noise ? 6.6 nv/h z ? 0.6 fa/ hz ? l o w off s et v o ltage (1.0 m v ma x) ? w i de s u p p ly v o ltage r a nge: 5 v t o 24 v ? no phase r e v e r s al ? l o w input c a pa citanc e ? single -sup ply and r a i l -to - r a il o u tput ? ex c e llen t dis t or tion specs: sfdr 95 db c @ 1 mhz ? high c o mmon-mode r e jec t ion r a tio: C106 db ? l o w po w e r: 6.5 ma t y pic a l s u p p ly current ? lo w co s t ? small pack aging: so t - 23-5 applic ation s ? phot odiode pr eamplifier ? p r ecision high gain amplifier ? high gain, high bandwidth c o mposit e amplif ier general de scription th e AD8067 f a s t fet ? am p is a vol t age fe e d b a ck am pl if ier w i t h fet in p u ts o f f e rin g wide b a n d wid t h (54 mh z @ g = +10) a n d hig h s l e w ra te (640 v/s). th e AD8067 is fa b r ica t e d in a p r o p r i eta r y , die le ctr i ca l l y is o l a t e d ex tra f a s t c o m p lem e n t a r y b i p o l a r p r o c es s (xfcb) t h a t ena b les hig h s p e e d , l o w p o wer , a n d hig h p e r f o r m a n ce fet in p u t am pli f iers. th e AD8067 is d e sig n e d to wo rk in a p plica t io n s t h a t r e q u i r e hig h s p e e d a n d lo w in p u t b i as cur r en t, s u c h as fas t p h o t odiode p r e a m p lif i ers. a s r e q u ir e d b y ph o t odiode a p pli c a t io n s , t h e las e r t r i m m e d ad806 7 has e x ce l l en t d c v o l t a g e o f fset (1.0 mv max) an d dr if t (15 v/c max). connection diagram +v s 5 4 1 2 3 ?in +in ?v s v out sot-23-5 (rt-5) f i gure 1. conne c t ion d i agr a m ( t op vie w ) th e fet in p u t b i as cur r en t (5 pa max) a n d lo w v o l t a g e no ise (6.6 nv/ h z ) a l s o co n t r i b u te to ma kin g i t a p p r o p r i a t e f o r p r e c isi o n a p plica t io n s . w i t h a wide s u p p ly v o l t ag e ran g e (5 v to 24 v) an d ra i l -to-ra i l o u t p u t , t h e AD8067 is wel l s u i t e d to a va r i ety o f a p plica t io n s t h a t r e q u ir e wide d y n a mic ran g e an d lo w dis to r t io n. th e AD8067 a m plif ier co n s u m e s o n l y 6.5 ma o f su p p l y cur r en t, w h i l e ca p a b l e o f deli v e r i n g 30 ma o f load cur r en t an d dr i v in g ca p a ci t i v e loads o f 100 pf . th e AD8067 a m plif ier is a v a i la b l e in a so t - 23-5 p a c k a g e a n d is ra t e d t o o p era t e o v er t h e in d u s t r i a l tem p era t ur e ra n g e, C40c to +85 c. frequency ? mhz gain ? db 28 8 10 12 14 16 18 20 22 24 26 0.1 1 1 0 100 g = +20 g = +10 g = +8 fi g u r e 2 . s m a l l s i g n a l fr e q u e n c y r e s p o n s e rev. 0 in fo rmation furn is h e d by an al o g dev i ces is believed to be a ccu rate and r e liable. how e ver, no r e spons i bili ty is assumed by analog devices fo r its use, nor f o r an y i n fri n geme nt s of p a t e nt s or ot her ri g h t s o f th ird parties th at may result fro m its use . specifications subject to chan g e witho u t n o tice. no licen s e is g r an te d by implicati o n or ot he rwi s e un der a n y p a t e nt or p a t e nt r i ghts of anal og de vices. trad emarks an d registered tra d ema r ks are the proper ty of th eir respectiv e co mpan ies. one technolog y way, p.o . box 9106, norwood, ma 02062-9106, u.s.a. t e l: 781. 329. 4 700 www.analog.com fax: 781. 326. 87 03 ? 2002 analog de vices, i n c. al l r i ght s r e ser v ed .
AD8067 table of contents AD8067Cs p e cif i ca t i o n s fo r 5 v ........................................................... 4 AD8067Cs p e cif i ca t i o n s fo r +5 v ........................................................... 5 AD8067Cs p e cif i ca t i o n s fo r 12 v ......................................................... 6 a b s o l u te m a xim u m r a t i n g s .................................................................. 7 m a xim u m p o wer dis s i p a t io n ............................................................ 7 t y p i ca l p e r f o r man ce c h aracter is t i cs .................................................... 8 t e s t cir c ui ts ............................................................................................ 13 th e o r y o f o p era t io n ............................................................................. 15 b a sic f r e q uen c y res p o n s e ............................................................... 15 resis t o r s e le ct io n f o r w ideb a n d o p era t io n .................................. 16 i n p u t an d o u t p u t o v erload b e ha vi o r ............................................ 17 i n p u t p r o t e c t i o n ................................................................................ 18 c a paci t i v e l o ad dr i v e ...................................................................... 18 l a yo u t , g r o u n d i n g, an d b y p a s s in g c o n s idera t i o n s ..................... 18 a p plica t io n s ............................................................................................ 20 w ideb a n d p h o t o diode p r e a m p ....................................................... 20 u s in g t h e ad80 67 a t gain s o f l e s s than 8 ................................... 21 s i n g le-s u p ply op era t io n .................................................................. 22 h i g h gain, h i g h b a n d wid t h c o m p osi t e am p l if i e r . . . . . . . . . . . . . . . . . . . . . . 22 o u t l in e dimen s i o n s .............................................................................. 24 or der i n g g u id e ................................................................................. 24 tables t a b l e 1. re co mm en de d v a l u es o f r g and r f ..................................... 15 t a b l e 2. rms n o is e c o n t r i b u t i o n s o f pho t o diode p r e a m p ............. 20 t a b l e 3. or d e r i n g g u ide ........................................................................ 24 revisi on h i s t or re visio n 0: i n i t ia l v e rsio n rev. 0 | page 2 of 2 4
AD8067 rev. 0 | page 3 of 2 4 figures figure 1. connection diagram (top view) ..........................................1 figure 2. small signal frequency response .........................................1 figure 3. maximum power dissipation vs. temperature for a 4-layer board ...............................................................................7 figure 4. small signal frequency response for various gains .........8 figure 5. small signal frequency response for various supplies .....8 figure 6. large signal frequency response for various supplies .....8 figure 7. 0.1 db flatness frequency response ...................................8 figure 8. small signal frequency response for various c load .........8 figure 9. frequency response for various output amplitudes ........8 figure 10. small signal frequency response for various r f .............9 figure 11. distortion vs. frequency for various loads ......................9 figure 12. distortion vs. frequency for various amplitudes .............9 figure 13. open-loop gain and phase ................................................9 figure 14. distortion vs. frequency for various supplies ..................9 figure 15. distortion vs. output amplitude for various loads ........9 figure 16. small signal transient response 5 v supply ...................10 figure 17. output overdrive recovery ...............................................10 figure 18. long-term settling time ...................................................10 figure 19. small signal transient response 5 v supply ...............10 figure 20. large signal transient response .......................................10 figure 21. 0.1% short-term settling time ........................................10 figure 22. input bias cu rrent vs. temperature ..................................11 figure 23. input offset voltage histogram ........................................11 figure 24. voltage noise ........................................................................11 figure 25. input bias current vs. common-mode voltage ..............11 figure 26. input offset voltage vs. common-mode voltage ...........11 figure 27. cmrr vs. frequency ..........................................................11 figure 28. output impedance vs. frequency .....................................12 figure 29. output saturation voltage vs. output load current ......12 figure 30. psrr vs. frequency .............................................................12 figure 31. quiescent current vs. temperature for various supply voltages ..............................................................................12 figure 32. output saturation voltage vs. temperature .................... 12 figure 33. open-loop gain vs. load current for various supplies .......................................................................................... 12 figure 34. standard test circuit .......................................................... 13 figure 35. open-loop gain test circuit ........................................... 13 figure 36. test circuit for capacitive load ....................................... 13 figure 37. cmrr te st circuit ............................................................. 14 figure 38. positive psrr test circuit ................................................. 14 figure 39. output impedance test circuit ........................................ 14 figure 40. noninverting gain configuration ................................... 15 figure 41. open-loop fr equency response .................................... 15 figure 42. inverting gain configuration ........................................... 15 figure 43. input and board capacitances .......................................... 16 figure 44. op amp dc error sources .............................................. 17 figure 45. simplified input schematic ............................................. 17 figure 46 current limiting resistor .................................................. 18 figure 47. guard-ring configurations .............................................. 18 figure 48. guard-ring layout sot-23-5 .......................................... 18 figure 49. wideband photodiode preamp ......................................... 20 figure 50. photodiode voltage noise contributions ....................... 20 figure 51. photodio de preamplifier ................................................... 21 figure 52. photodiode preamplifier frequency response .............. 21 figure 53. photodiode prea mplifier pulse response ....................... 21 figure 54. gain of less than 2 schematic .......................................... 21 figure 55. gain of 2 pulse response .................................................. 22 figure 56. single-supply operation schematic ................................ 22 figure 57. AD8067/ad 8009 composite ........................................... 23 figure 58. gain bandwidth response ................................................ 23 figure 59. large signal response ........................................................ 23 figure 60. small signal response ........................................................ 23 figure 61. 5-lead plastic surface mount package ........................... 24
AD8067 rev. 0 | page 4 of 24 AD8067?specifications for 5 v v s = 5 v (@ t a = +25c, g = +10, r f = r l =1 k, unless otherwise noted.) parameter conditions min typ max unit v o = 0.2 v p-p 39 54 mhz ?3 db bandwidth v o = 2 v p-p 54 mhz bandwidth for 0.1 db flatness v o = 0.2 v p-p 8 mhz output overdrive recovery time (pos/neg) v i = 0.6 v 115/190 ns slew rate v o = 5 v step 500 640 v/s dynamic performance settling time to 0.1% v o = 5 v step 27 ns f c = 1 mhz, 2 v p-p 95 dbc f c = 1 mhz, 8 v p-p 84 dbc f c = 5 mhz, 2 v p-p 82 dbc spurious free dynamic range (sfdr) f c = 1 mhz, 2 v p-p, r l = 150 : 72 dbc input voltage noise f = 10 khz 6.6 nv/hz noise/distortion performance input current noise f = 10 khz 0.6 fa/hz input offset voltage 0.2 1.0 mv input offset voltage drift 1 15 v/c 0.6 5 pa input bias current t min to t max 25 pa 0.2 1 pa input offset current t min to t max 1 pa dc performance open-loop gain v o = 3 v 103 119 db common-mode input impedance 1000||1.5 g||pf differential input impedance 1000||2.5 g||pf input common-mode voltage range ?5.0 2.0 v input characteristics common-mode rejection ratio (cmrr) v cm = ?1 v to +1 v ?85 ?106 db r l = 1 k ?4.86 to +4.83 ?4.92 to +4.92 v output voltage swing r l = 150 ?4.67 to +4.72 v output current sfdr > 60 dbc, f = 1 mhz 30 ma short circuit current 105 ma output characteristics capacitive load drive 30% over shoot 120 pf operating range 5 24 v quiescent current 6.5 6.8 ma power supply power supply rejection ratio (psrr) ?90 ?109 db
AD8067 AD8067?specifications for +5 v v s = +5 v (@ t a = + 25c, g = + 10, r l =r f = 1 k, unles s other w is e n o ted. ) param e t e r c o n d i t i o n s m i n t y p m a x u n i t v o = 0.2 v p-p 3 6 5 4 m h z C3 db band width v o = 2 v p-p 5 4 m h z bandwidt h for 0.1 db flatness v o = 0.2 v p-p 8 m h z output overdrive recovery time (pos/neg) v i = +0. 6 v 1 5 0 / 2 0 0 n s sle w rate v o = 3 v step 3 9 0 4 9 0 v / s dyn a mic per f or man c e settling time to 0.1% v o = 2 v step 2 5 n s f c = 1 mhz, 2 v p- p 86 dbc f c = 1 mhz, 4 v p- p 74 dbc f c = 5 mhz, 2 v p- p 60 dbc spurious free dy namic range (sfdr) f c = 1 mhz, 2 v p- p, r l = 150 ? 72 dbc input vo ltage noise f = 10 k h z 6.6 nv/ hz n o ise/ dis t or ti on per f or man c e input current no ise f = 10 k h z 0.6 fa/h z input offset volt age 0 . 2 1 . 0 m v input offset volt age drift 1 1 5 v / c 0 . 5 5 p a input bias current t min to t max 2 5 p a 0 . 1 1 p a input offset current t min to t max p a dc per f or man c e open -loo p gain v o = 0.5 v to 4.5 v 1 0 0 1 1 7 d b common-mode i n put impedan c e 1000| |2.3 g?||pf differential input impedance 1000| |2.5 g?||pf input common - mode voltage range 0 2.0 v inpu t characteristic s common- mode rej e c t ion ratio (cmrr) v cm = 0.5 vto 1.5 v C81 C98 db r l = 1 k? 0.07 to 4.8 9 0.03 to 4.9 4 v output vol t age sw ing r l =150 ? 0.08 to 4.8 3 v output current sfdr > 6 0 db c, f = 1 m h z 22 ma short circuit current 95 ma out p u t characteristic s capacitive load drive 30% over shoot 120 pf operating range 5 24 v quiescent current 6.4 6.7 ma power s u p p l y po wer supp ly re jectio n ratio (ps rr) C87 C103 db rev. 0 | page 5 of 2 4
AD8067 AD8067?specifications for 12 v v s = 12 v (@ t a = + 25c, g = + 10, r l = r f = 1 k , unless otherwis e noted . ) param e t e r c o n d i t i o n s m i n t y p m a x u n i t v o = 0.2 v p-p 3 9 5 4 m h z C3 db band width v o = 2 v p-p 5 3 m h z bandwidt h for 0.1 db flatness v o = 0.2 v p-p 8 m h z output overdrive recovery time (p os/neg) v i = 1 .5 v 75/1 80 ns sle w rate v o = 5 v step 5 0 0 6 4 0 v / s dyn a mic per f or man c e settling time to 0.1% v o = 5 v step 2 7 n s f c = 1 mhz, 2 v p- p 92 dbc f c = 1 mhz, 2 0 v p-p 84 dbc f c = 5 mhz, 2 v p- p 74 dbc spurious free dy namic range (sfdr) f c = 1 mhz, 2v p- p, r l = 150 ? 72 dbc input vo ltage noise f = 10 k h z 6.6 nv/ hz n o ise/ dis t or ti on per f or man c e input current no ise f = 10 k h z 0.6 fa/h z input offset volt age 0 . 2 1 . 0 m v input offset volt age drift 1 1 5 v / c 1 . 0 5 p a input bias current t min to t max 2 5 p a 0 . 2 1 p a input offset current t min to t max p a dc per f or man c e open -loo p gain v o = 10 v 1 0 7 1 1 9 d b common-mode i n put impedan c e 1000| |1.5 g?||pf differential input impedance 1000| |2.5 g?||pf input common - mode voltage range C12.0 9.0 v inpu t characteristic s common- mode rej e c t ion ratio (cmrr) v cm = C1 v to +1 v C89 C108 db r l = 1 k? C11.70 to +1 1.70 C11.85 to +1 1.84 v output vol t age sw ing r l = 500 ? C11.31 to +1 1.73 v output current sfdr > 6 0 db c, f = 1 m h z 26 ma short circuit current 125 ma out p u t characteristic s capacitive load drive 30% over shoot 120 pf operating range 5 24 v quiescent current 6.6 7.0 ma power s u p p l y p o w e r suppl y re j e c t ion ratio (p srr) C86 C97 db rev. 0 | page 6 of 2 4
AD8067 absolute maximum ratings param e t e r r a t i n g supply voltage 26.4 v po wer dissipatio n see figure 3 common- mode input vol t age v ee C 0.5 v to v cc + 0.5 v dif f e r e ntia l inpu t v o lta g e 1. 8 v storage temperature C65c to + 125c operating temp erature range C40c to + 85c lead t e mperature range (soldering 10 se c ) 300c junc tion temper ature 150c st res s es a b ove t h o s e li st ed un der ab so lut e ma xi m u m r a t in gs m a y ca us e permanent d amage to the d e vice. this is a s t ress rating onl y and f u nctional o p e r atio n o f the device at the s e o r any o the r co nd itio ns a b o v e tho se i n di ca t e d i n t h e op era t i o n a l sect i o n of this s p ecif ication is not impl i ed . expos ure t o a b s o lu t e m a x imum rating co nd itio ns fo r e x tend e d pe riod s may af f e ct d e vice rel iabil ity. maximum power dissipation th e as socia t e d ra ise in j u n c t i o n tem p e ra t u r e (t j ) o n t h e die limi ts t h e ma xim u m sa f e p o wer dis si p a tio n in t h e AD8067 p a c k a g e. a t a p p r o x i m a t e l y 1 5 0 c , wh i c h i s th e gl a s s tr a n s i ti o n t e m p e r a t u r e , th e p l as t i c wil l c h a n g e i t s p r o p er t i es. e v en t e m p o r a r il y ex ce e din g t h is t e m p era t u r e li mi t ma y c h a n g e t h e s t r e s s es t h a t t h e p a c k a g e ex e r ts o n t h e die , p e r m a n en t l y s h ift i n g th e p a ra m etr ic p e r f o r ma n c e o f t h e AD8067. e x ce e din g a j u n c t i o n tem p era t ur e o f 17 5c f o r a n exten d e d per i od o f t i m e ca n r e s u l t in c h a n g e s in th e si lico n de vi ces, p o ten t ia l l y ca usi n g fai l ur e. th e p o w e r d i s s i p a t e d in t h e p a c k a g e ( p d ) i s th e s u m o f th e q u ies c en t p o wer dis si p a t i o n an d t h e p o wer dis si p a te d in t h e p a c k a g e d u e t o th e load dr i v e . th e q u iescen t p o w e r is t h e v o l t a g e betw e e n t h e s u p p l y p i n s ( v s ) t i m e s t h e q u i e scen t cur r en t ( i s ). assu m i ng t h e l o a d ( r l ) is r e f e r e n c e d to mids u p ply , t h e to t a l dr i v e po w e r i s v s /2 i ou t , s o me o f w h ic h is dis si p a te d in t h e p a c k ag e and s o me in t h e l o a d ( v ou t i out ). th e dif f e r e n c e betw e e n t h e to t a l dr i v e p o wer an d t h e load p o wer is t h e dr i v e p o wer dis si p a t e d in t h e p a c k a g e. rms o u t p u t v o l t ag es s h o u ld b e co n s ider e d . () power load C power drive total power quiescent p d + = () l out l out s s s d r v C r v v i v p 2 2 ? ? ? ? ? ? ? ? + = if r l is r e f e r e n c e d to v s C as in sin g le-s u p p l y o p era t io n, t h en t h e to t a l dr ive p o wer is v s i ou t . i f t h e rms signal le v e ls a r e in det e r m i n a t e , t h en co n s ider t h e w o r s t cas e , w h en v ou t = v s /4 f o r r l to m i dsu p pl y : () () l s s s d r / v i v p 2 4 + = in s i n g l e - s u p p l y op e r at i o n w i t h r l re fe re nc e d t o v sC , wo rst ca s e is v ou t = v s /2. ai r f lo w wi l l in cr e a s e h e a t dis s i p a t io n ef f e ct i v el y , r e d u cin g ja . i n a d d i ti o n , m o r e m e tal d i r e ctl y i n c o n t a c t w i th th e pa c k a g e l e a d s fr o m m e tal tr a c e s , th r o u g h h o l e s , gr o u n d , a n d p o w e r p l a n e s w i ll re du c e t h e ja . f i gur e 3 s h o w s t h e maxim u m s a f e p o w e r dis s i p a t i o n in t h e p a c k - a g e v e rs us a m b i en t tem p era t ur e f o r t h e so t - 23-5 (180c/w) p a ckage o n a je dec st andar d 4 - l a ye r b o ar d. ja val u es a r e a p p r o x im a t io n s . i t s h o u ld b e no te d t h a t f o r e v er y 10c r i s e in tem p era t ur e, i b a ppro x i m a t e l y do u b l e s ( s e e f i g u re 2 2 ) . 4 0 2.0 1.5 0.5 0 0 ambient temperature c maximum power dissapation w 1.0 3 0 20 10 8 0 10 20 30 40 50 60 70 sot-23-5 f i g u re 3. m a x i m u m p o wer d i s s i pat i on v s . t e mpe r at u r e f o r a 4-laye r b o a r d rev. 0 | page 7 of 2 4
AD8067 rev. 0 | page 8 of 2 4 typical performance characteristics default conditions v s = 5 v ( t a = + 25 c, g = + 10, r l = r f = 1 k , unless otherwise noted . ) frequency mhz gain db 28 8 10 12 14 16 18 20 22 24 26 1 1 0 100 g = +20 g = +10 g = +6 g = +8 v out = 200mv p-p f i g u r e 4. s m al l s i g n al f r equenc y r e s p ons e f o r v a r i ous g a ins frequenc mhz gain db 22 14 15 16 17 18 19 20 21 1 1 0 100 v out = 200mv p-p v s = f i g u re 5. s m a l l sig n al f r equenc y r e s p ons e f o r v a r i ous s u p p li es frequenc mhz gain db 22 14 15 16 17 18 19 20 21 1 1 0 100 v out = 2v p-p v s = f i g u re 6. la r g e s i g n al f r equenc y r e s p ons e f o r v a r i ous s u p p li es frequenc mhz gain db 20.7 19.8 19.9 20.0 20.1 20.2 20.3 20.4 20.5 20.6 1 1 0 100 v out = 0.2v p-p v out = 0.7v p-p v out = 1.4v p-p f i gur e 7 . 0 . 1 db f l atness f r equenc y resp o n se frequenc mhz gain db 24 14 15 16 17 18 19 20 21 22 23 1 1 0 100 v out = 200mv p-p c l = 100pf c l = 25pf c l = 100pf r snub = 24.9 ? f i g u re 8. s m a l l sig n al f r equenc y r e s p ons e f o r v a r i ous c lo a d frequenc mhz gain db 22 14 15 16 17 18 19 20 21 1 1 0 100 v out = 0.2v p-p, 2v p-p v out = 4v p-p f i gur e 9 . f r equenc y resp o n se for v a rio u s o u tput a m pli t udes
AD8067 rev. 0 | page 9 of 2 4 frequency mhz gain db 22 14 15 16 17 18 19 20 21 1 1 0 100 r f = 1k ? ? ? f i g u re 10. sm a ll s i g n al f r equenc y r e s p ons e f o r v a r i ous r f frequenc mhz distortion dbc 40 140 130 120 110 100 90 80 70 60 50 0.1 1 1 0 100 hd2 r load = 150 ? ? ? ? f i gure 11. d i s t o r tio n v s . f r equ e nc y fo r v a ri ous l o ads frequenc mhz distortion dbc 2 0 140 120 100 8 0 6 0 4 0 0.1 1 1 0 100 v s = f i gure 12. d i s t o r tio n v s . f r equ e nc y fo r v a ri ous a m pl itude s frequenc mhz gain db 90 0 10 20 30 40 50 60 70 80 10 phase degrees 120 150 120 90 60 30 0 30 60 90 180 0.01 0.1 1 1 0 100 1k phase gain f i gure 13. o p en-l oop g a in and phase frequenc mhz distortion dbc 40 50 60 70 80 90 100 110 120 130 140 0.1 1 1 0 100 hd3 v s = f i gure 14. d i s t o r tio n v s . f r equ e nc y fo r v a ri ous su p p l i es output amplitude v p-p distortion dbc 30 120 110 100 90 80 70 60 50 40 130 0 2 4 6 8 10 12 14 16 18 20 22 24 v s = ? ? ? ? f i gur e 1 5 . di stor ti on vs . output a m pl i t ude for v a r i o u s l oads
AD8067 rev. 0 | page 10 of 24 g = +10 v in = 20mv p-p 50mv/div 25ns/div 1.5v f i g u re 16. sm a ll s i g n al t r ans i ent r e s p ons e 5 v su p p ly 2v/div 10v in v out 200ns/div g = 10 f i gure 17. o u tput o v er dr ive r e c o ver y 0.1% 0.1% v in (100mv/div) v out 10v in (5mv/div) 5 f i gure 1 8 . l o ng- t erm s e ttl ing ti me 50mv/div 25ns/div g = 10 v in = 20mv p-p c l = 100pf c l = 0pf f i g u re 19. sm a ll s i g n al t r ans i ent r e s p ons e 5 v su p p ly 5v/div 50ns/div v s = f i g u re 20. lar g e s i g n al t r ans i ent r e s p ons e 0.1% 0.1% t = 0 v out (1v/div) g = 10 v in (100mv/div) v out 10v in (5mv/div) 5ns/div f i g u re 21. 0 . 1% sh or t - t e r m s e t t l i n g ti me
AD8067 temperature ? c input bias current ? pa 14 v s = 5v 12 10 8 6 4 2 0 25 35 45 55 65 75 85 rev. 0 | page 11 of 24 v s = 12v common-mode voltage v input bias current pa 10 1 0 8 6 4 2 0 2 4 6 8 1 4 1 2 1 0 8 6 4 2 02468 1 0 1 2 1 4 v s = f i g u re 25. input b i a s current v s . co mm on-m od e v o lt ag e f i gure 22. input b i a s current v s . t e mpe r ature common-mode voltage v input offset voltage mv 5 5 4 6 2 1 0 1 2 3 4 14 12 1 0 8 6 4 2 0 2 4 6 8 10 12 14 v s = input offset voltage mv 1800 0 200 400 600 800 count 1000 1200 1400 1600 1 0 1 n = 12255 sd = 0.203 mean = 0.033 f i g u re 26. input o f f s et v o lt ag e v s . co m m o n -m ode v o lt ag e f i gure 23. input o f f s et v o ltag e histogr a m frequenc mhz cmrr db 40 120 110 100 90 80 70 60 50 0.1 10 1 100 frequenc hz noise nv/ hz 1000 10 100 1 1 1 0 100 1k 10k 100k 1m 10m 100m fi g u r e 2 7 . c m r r v s . fr e q u e n c y f i g u re 24. v o lt ag e nois e
AD8067 frequency ? mhz output impedance ? ? rev. 0 | page 12 of 24 g = +10 temperature f i gure 31. q u ies c e n t current v s . t e mp er at u r e f o r v a r i ous sup p ly v o lt ag es f i gure 28. o u tput imped a nce v s . f r eq uenc y (v cc v oh ), (v ol v ee ), v s = ? i load ma out p ut s a t urat ion v o l t a ge v 0.30 0 0.05 0.10 0.15 0.20 0.25 0 5 10 15 20 25 30 35 40 v cc v oh v ol v ee f i g u re 32. o u t p ut s a t u r a t i on v o lt ag e v s . t e mper at ure f i gure 2 9 . o u tput s a tur a t i o n v o l t a g e vs . o u tput l o a d c u rr ent i load m a open-loop gain db 140 50 60 70 80 90 100 110 120 130 0 5 10 15 20 25 30 35 40 v s = frequenc mhz psrr db 0 100 90 80 70 60 50 10 30 20 10 0.01 0.1 1 1 0 100 psrr psrr fi g u r e 3 0 . p s r r v s . fr e q u e n c y f i gure 33. o p en-l o o p g a in v s . l o ad current for v a ri ous s u p p l i es
AD8067 rev. 0 | page 13 of 24 test circuits 5 2 3 1 4 AD8067 110 ? ? ? ? f i gure 34. stand a rd t e s t ci r c u i t 5 2 3 1 4 AD8067 110 ? ? ? ? f i gure 35. o p en-l oop g a in t e st cir c uit 5 2 3 1 4 AD8067 110 ? ? ? ? f i gure 36. t e s t c i rc uit for cap a c i tive l oad
AD8067 5 2 3 1 4 AD8067 110 ? ? ? ? ? f i g u re 37. c m r r t e s t cir c u i t 5 2 3 1 4 AD8067 110 ? ? ? ? f i gur e 3 8 . p o si t i v e p s rr t e st cir c ui t 5 2 3 1 4 AD8067 110 ? ? ? f i gure 39. o u tput imped a nce t e s t circ uit rev. 0 | page 14 of 24
AD8067 rev. 0 | page 15 of 24 theory of operation frequency mhz ga in db phase deg r ees 90 0 10 20 30 40 50 60 70 80 10 120 150 120 90 60 30 0 30 60 90 180 0.01 0.1 1 1 0 100 1k phase gain th e AD8067 is a lo w n o is e, wideb a n d , vo l t a g e f e e d b a c k o p era t io na l am plif ier tha t co m b in es a p r e c isio n j f et in p u t s t ag e wi t h analog dev i c e s d i e l ectri c all y i s o l a t ed e x t r a f a s t c o m p l e m e n t a r y b i po l a r (xfcb) p r oces s bjt s . op era t in g s u p p l y v o l t a g es r a n g e f r o m 5 v t o 24 v . th e a m p l if ier f e a t u r es a pa t e n t e d ra il-t o - ra il o u t p u t s t a g e ca p a b l e o f dr i v ing wi t h in 0.25 v o f ei t h er p o w e r s u p p l y w h il e s o ur cin g o r sin k in g 30 ma. th e jfet in p u t, co m p os e d o f n-c h a n n e l de vices, has a co mm o n -mode in p u t ra n g e t h a t in c l udes th e n e g a ti v e s u p p l y r a il a n d e x t e n d s t o 3 v be l o w th e po s i ti v e s u p p l y . i n addi t i o n , t h e p o t e n t ia l f o r phas e r e v e r s al be ha vio r has b e en elimina t e d f o r a l l in p u t v o l t ag es wi t h in t h e po wer s u p p li es. th e co mb ina t io n o f lo w no is e, d c p r e c isio n, an d hig h b a n d wid t h ma k e s t h e ad80 67 uniq uel y s u i t ed f o r wideb a n d , v e r y hig h in p u t im p e dan c e, hig h gain b u f f er a p pli c a t io n s . i t wi l l a l s o p r o v e us ef u l in wideb a n d t r a n sim p e d an ce a p plica t io n s , s u c h a s a ph o t odi o de in ter f ace, t h a t r e q u ir e v e r y lo w in p u t curr en ts an d dc p r e c isio n. f i gure 41. o p en-l oop f r equ e nc y response b a sic fre q u e nc y re sp onse th e ba n d wid t h f o r m u l a o n l y h o l d s tr ue w h en t h e p h ase ma r g in o f t h e a p plica t io n a p p r oac h es 90, w h ic h i t wi l l in hig h gain co nf ig - ura t io n s . th e b a n d wid t h o f t h e AD8067 us e d in a g = +10 b u f f er is 54 mh z, co n s idera b l y fas t er th a n t h e 30 mh z p r e d icte d b y t h e c l o s ed l o o p C 3 db fr eq u e n c y eq u a ti o n . t h i s e x t e n d ed ba n d w i d t h i s d u e to t h e phase ma rg in b e in g a t 60 in s t e a d o f 9 0 . gain s lo wer t h a n +10 wi l l s h o w a n in cr e a s e d a m o u n t o f p e a k in g, as s h o w n in f i gur e 4. fo r ga i n s lo w e r t h a n +7 , us e t h e ad8065 , a uni t y ga in s t a b le jfet in p u t o p a m p wi t h a uni t y ga in b a n d wid t h o f 145 mh z, o r r e f e r to t h e a p plica t io n s s e ct io n fo r usin g t h e AD8067 in a ga in o f 2 co nf igura t io n. th e AD8067 s typ i ca l o p en-lo o p r e s p o n s e (s e e f i gur e 41) s h o w s a phas e ma rg in o f 60 a t a ga in o f + 10. t y p i ca l co nf i g ura t io n s f o r n o nin v er t i n g an d in v e r t in g v o l t ag e gain a p plica t io n s ar e s h o w n in f i gur e 40 a n d f i gur e 42. t h e c l o s ed - l oo p fr eq u e n c y r e s p o n se o f a ba s i c n o n i n v e r ti n g g a i n co nf igura t io n can b e a p p r o x ima t e d usin g t h e e q ua t i o n : () () g f g r r r gbp frequency db C loop closed + = 3 g a i n r g (? ) r f (k ? ) b w (mh z ) 1 0 1 1 0 1 5 4 2 0 4 9 . 9 1 1 5 5 0 2 0 1 6 1 0 0 1 0 1 3 1 + = g f /r r gain dc gb p is t h e gain b a n d wid t h p r od uct o f t h e am plif ier . t y p i ca l gb p f o r t h e AD8067 is 300 mh z. s e e t a b l e 1 f o r r e co mm en de d va l u es of r g and r f . t a bl e 1 . r ecom m e nded v a lues of r g and r f 1 r r gain noise ion configurat ng noninverti g f + = v s AD8067 r r load v out r f 10 v s AD8067 r r load v ou t r f for best performance, set r s r = r g || r f 10 f i gure 40. nonin v e r ting g a in conf ig u r at i o n f i g u re 42. inve r t ing g a i n co nf ig ur at i o n
AD8067 rev. 0 | page 16 of 24 f o r in v e r t in g v o l t ag e gain a p plica t io n s , t h e s o ur ce im p e dan c e o f t h e i n p u t s i gn al m u s t be co n s i d er ed bec a use th a t will set th e a p p l i c a- ti o n s n o i s e g a i n a s w e ll a s th e a p pa r e n t c l o s ed - l oo p g a i n . t h e ba s i c f r e q uen c y e q ua t i o n fo r in v e r t in g a p plica t io n s is b e lo w . v i r s signal source + + v ou t + c par c par r g c d c m c m r f s g f s g r r r r r (gbp) frequency db C loop closed + + + = 3 s g f r r r C gain dc + = f i gure 43. input an d boar d cap a citan c es gb p is t h e gain b a n d wid t h p r od uct o f t h e am plif ier , an d r s is t h e sig n a l s o ur ce r e si s t a n ce. th er e wi l l b e a po le in t h e f e e d b a c k lo o p r e s p o n s e f o r m e d b y t h e s o ur ce im p e dan c e s e en b y t h e am plif ier s n e ga t i v e in p u t (r g ?? r f ) a n d t h e s u m o f t h e a m p l if ie r s dif f er en t i a l in p u t ca p a ci t a n c e , co mmo n - mo de in p u t ca p a ci t a nce, and an y b o ar d p a rasi t i c ca p a ci t a nce. t h is wi l l de cr e a s e t h e lo o p phas e ma r g in and can ca u s e st ab i l i t y pr obl e ms , i.e., u n a cce pt abl e p e a k ing and r i ng ing i n th e r e s p o n se . t o a v o i d th i s p r o b l e m i t i s r e c o m m e n d e d th a t th e r e sis t a n ce a t t h e AD8067 s n e ga t i v e in p u t b e k e p t b e lo w 200 ? fo r a l l wid e b a n d v o lt ag e gain a p plica t io n s . s g s g f r r r r r gain noise ion configurat inverting + + + = i t is im p o r t an t th a t t h e n o is e gain f o r in v e r t in g a p p l ica t io n s b e k e p t a b o v e 6 f o r s t a b il i t y r e aso n s. i f t h e signa l so ur ce dr i v in g t h e in v e r t e r is an o t h e r am plif ier , t a k e car e t h a t t h e dr i v in g am p l if ier s h o w s lo w o u t p u t im p e da nce t h r o ugh t h e f r e q uen c y s p a n o f t h e expe ct e d c l os e d -lo o p b a nd wid t h o f t h e AD8067. m a tc hin g t h e im p e da n c es a t t h e in p u ts o f t h e AD8067 is a l s o r e co mmen de d f o r wideb a n d v o l t ag e gain a p plica t io n s . this wi l l minimize no n l ine a r co mmo n - m o d e ca p a ci t i v e ef f e c t s t h a t can sig n if ican t l y degrade s e t t lin g t i m e an d dis t o r t i o n p e r f o r man c e. resistor selection for wideband op eration v o l t a g e f e e d bac k a m p l if ie r s ca n u s e a wide ra n g e o f r e sis t o r va l u es t o set t h eir ga in. p r o p er design o f t h e a p p l ica t io n s f e e d bac k n e two r k r e q u ir es co n s idera t io n o f t h e f o l l o w in g is sues: th e AD8067 has a lo w in p u t v o l t a g e n o is e o f 6.6 nv/ hz . s o u r c e r e sis t a n ces g r e a t e r tha n 500 ? a t ei t h er in p u t t e rm ina l wil l n o t a b l y in cr e a se t h e a p pa r e n t ref e r r e d t o i n p u t (r ti) v o l t a g e n o ise o f t h e ap p l i c at i o n . ? p o l e s f o rm ed b y th e a m p l i f i e r s i n p u t c a pa c i ta n c e s w i th th e r e sis t a n ces s e en a t t h e a m plif i e r s in p u t termin a l s ? ef f e cts o f misma t c h e d s o ur ce im p e da n c es th e a m p l if i e r m u s t s u p p l y o u t p u t cur r en t t o i t s f e e d bac k n etw o r k, as w e l l as t o t h e i d en t i f i e d load . f o r in s t a n ce , t h e load r e sis t a n ce p r es en t e d to t h e am plif ier in f i gur e 40 is r lo a d ?? (r f + r g ). f o r a n r lo a d o f 100 ?, r f of 1 k ? , a n d r g o f 100 ?, t h e am plif ier wi l l b e dr i v in g a to t a l load r e s i s t an ce o f ab o u t 92 ?. this be co m e s mo r e o f an i ssu e a s r f d e cr e a s e s. th e ad 8067 is ra te d to p r o v ide 30 ma o f lo w dis t o r t i o n o u t p u t curr en t. h e a v y o u t p u t dr i v e r e q u ir em en ts al so i n c r ea se th e pa r t s po w e r d i s s i pa ti o n a n d s h o u l d be tak e n in to acco un t. ? r e s i s t or v a lu e i m p a c t on t h e ap p l i c at i o n s ou t p u t v o l t a g e no ise ? am plif i e r loadin g ef f e cts th e AD8067 has co mmo n - mode in p u t ca p a ci t a n c es (c m ) o f 1.5 pf a n d a dif f er en t i a l in p u t ca p a ci t a n c e (c d ) o f 2.5 pf . this is i l l u s t ra ted in f i gur e 43. th e s o ur ce im p e dance dr i v in g t h e p o si t i v e in p u t o f a n o nin v er t i n g b u ff er wi l l f o r m a po le p r im a r i l y wi th t h e a m plif i e r s co mmo n - mo de in p u t ca p a ci t a nce as wel l as a n y p a r a si t i c ca p a ci t a n c e d u e t o t h e boa r d la y o u t (c pa r ). th is wil l limi t t h e obt a i n a b l e b a n d w i dt h . f o r g = + 1 0 bu f f e r s , t h i s b a n d w i dt h l i m i t wi l l b e co m e a p p a r e n t f o r s o ur ce im p e da n c es >1 k ?.
AD8067 rev. 0 | page 17 of 24 dc error calculations input and outp ut ov erload behavior f i gur e 44 il l u s t ra t e s t h e p r im a r y d c er r o r s as s o cia t e d wi t h a v o l t a g e f e e d b a c k am plif ier . f o r b o t h in v e r t in g an d n o nin v er t i n g co nf igura t io n s : a sim p lif i e d s c h e ma t i c o f t h e ad 8067 in p u t s t a g e is s h o w n in f i gur e 45. this s h o w s t h e cas c od e d n-c h ann e l jf et in p u t pair , t h e es d an d o t her p r o t e c t i o n dio d es, an d t h e a u xiliar y np n in p u t s t ag e t h a t e l imina t es phase in v e rsio n b e ha vi o r . ? ? ? ? ? ? ? ? + = g f g os os r r r v v to due error voltage output w h en t h e co mmo n-m o de in p u t vo l t a g e t o t h e a m p l if ier is d r i v en t o w i th i n a p p r o x i m a t e l y 3 v o f th e po s i ti v e po w e r s u p p l y , th e i n p u t jfet s b i as cur r en t wi l l t u r n o f f , a n d t h e b i as o f t h e np n p a ir wi l l t u r n o n , t a kin g o v er co n t r o l o f t h e a m p l if ier . th e npn dif f er en t i a l p a ir n o w s e ts t h e am plif ier s o f fs et, an d t h e in p u t b i as cur r en t is n o w in t h e ra n g e o f s e v e ra l ten s o f micr oa m p s. th is b e ha vi o r is i l l u s t ra te d in f i gur e 25 an d f i gur e 26. n o r m a l o p era t io n r e s u mes w h en t h e co mmo n-m o de vo l t a g e g o es be lo w t h e 3 v f r o m t h e p o s i t i ve supply t h re shol d. f C b g g f s b b r i C r r r r i i to due error voltage output ? ? ? ? ? ? ? ? + = + t o tal e r r o r i s th e s u m o f th e t w o . d c co mmo n- mode an d p o wer s u p p ly ef f e c t s can b e adde d b y m o de lin g t h e t o t a l v os w i th th e e x p r e s s i o n : cmr ?v psr ?v (nom) v (tot) v cm s os os + + = t h e o u t p u t tr a n s i s t o r s h a v e c i r c u i tr y i n c l u d ed t o l i m i t th e e x t e n t o f t h eir sa t u ra t i o n w h en t h e o u t p u t is o v er dr i v en. this im p r o v es ou t p u t r e c o v e r y t i m e . a p l ot of t h e ou t p u t r e c o v e r y t i m e f o r t h e AD8067 us e d as a g = +10 b u f f er is s h o w n in f i gu r e 17. v os (n o m ) is t h e o f fset v o l t a g e s p e c if ie d a t no mina l co n d i t io n s (1 mv max). ? v s is t h e c h a n g e in p o wer s u p p l y v o l t a g e f r o m no m i n a l cond i t i o ns . ps r is p o wer s u p p ly r e je ct io n (90 db minim u m). ? v cm is t h e c h a n g e i n co mm o n -mode v o l t a g e f r o m n o mina l tes t co ndi t io n s . cmr is co mm o n - m od e r e jectio n (85 d b minim u m f o r t h e AD8067). v bia s v cc v ee v ee v cc v p v n switch control v ee v cc to rest of amp v threshold v i r s r g i b i b v out v os r f f i gure 44. o p a m p dc e rror s o urc e s f i g u re 45. si mpl i f i e d input schema tic
AD8067 rev. 0 | page 18 of 24 input protection layout, grounding, and bypassing considerations th e in p u ts o f t h e AD8067 a r e p r o t e c te d wi t h b a ck-to-b a c k di odes betw e e n t h e in p u t t e r m in als as w e l l as es d diodes t o ei t h er p o w e r supp ly . t h e re su l t i s an i n put st age w i t h pi c o am p le ve l i n put cur r en ts tha t ca n wi t h s t a n d 2 kv es d e v en ts (h u m a n bod y mode l) wi t h n o degrada t io n. layout i n ext r em e l y lo w in p u t b i as cur r en t am plif ier a p plica t io n s , s t ra y le a k a g e cu r r en t p a t h s m u s t be k e p t t o a minim u m . an y v o l t a g e dif f er en t i a l betw e e n t h e a m p l if ie r in p u ts a n d n e a r b y t r aces wil l set u p a lea k a g e p a th t h r o ug h t h e pcb . c o n s ider a 1 v sig n a l a n d 100g ? t o gr o u nd p r esen t a t t h e in p u t o f t h e a m p l if ier . th e r e s u l t a n t le a k a g e cu r r en t i s 10 pa; t h is is t e n t i m e s t h e in p u t b i as cur r en t o f t h e am pl if ie r . p o o r pc b l a y o u t , c o n t am in a t io n , and t h e b o ar d ma t e r i a l ca n cr e a t e la r g e l e a k a g e curr en ts. c o mm o n co n t a m ina n ts o n b o ar ds ar e sk in o i l s , m o ist u r e , s o l d e r f l u x , and cl e a n i ng age n t s . th er ef o r e , i t is im p e ra t i v e t h a t th e boa r d be t h o r o u ghl y c l e a n e d a n d t h e b o ar d su r f a c e b e f r e e o f c o n t am in an t s to f u l l y t a k e a d van t age o f t h e AD8067 s lo w in p u t b i as cur r en ts. ex c e s s i v e po w e r d i s s i p a t i o n th r o u g h th e p r o t ecti o n d e v i c e s w i ll des t r o y o r degr a d e t h e p e r f o r m a n c e o f t h e a m p l ifier . dif f er en t i a l vol t age s g r e a te r t h an 0 . 7 v w i l l r e su l t in an in pu t c u r r e n t o f a ppro x i m a t e l y ( | v + C v C | C 0.7 v )/( r i + r g )), w h er e r i and r g are t h e r e s i s t o r s (se e f i gur e 46). f o r in p u t v o l t a g es be y o n d t h e p o si t i ve s u p p l y , t h e in p u t cur r en t wil l be a b o u t ( v i C v cc C 0.7 v )/ r i . f o r in p u t v o l t a g es be y o n d t h e n e ga t i ve s u p p l y , t h e in p u t curr en t wil l be ab o u t ( v i C v ee + 0.7 v )/ r i . f o r a n y o f t h ese co n d i t io n s , r i sh o u l d be size d t o limi t t h e r e s u l t in g in p u t curr en t t o 50 ma o r les s . v i r i > (v i v ee + 0.7v)/50ma r i > (v i v cc 0.7v)/50ma for v i beond suppl voltages v out + r g r f r i + AD8067 r i > ( |v+ v | 0.7v)/50ma for large |v + v | t o s i g n if ican t l y r e d u ce l e a k age p a t h s , a gu ar d r i ng/shiel d ar o u nd t h e in p u ts s h o u ld be use d . th e gua r d r i n g cir c les t h e in p u t p i n s a n d is dr i v en t o t h e sa m e p o t e n t ia l as t h e in p u t sign a l , t h er eb y r e d u cin g t h e p o t e n t ia l dif f er en ce betw e e n p i n s . f o r t h e gua r d r i n g t o be co m- p l et e l y ef f e ct i v e , i t m u s t be dr i v en b y a r e la t i v e l y lo w im p e da n c e s o ur ce a n d sh o u l d co m p letel y s u rr o u n d t h e in p u t le ads o n a l l si des, ab o v e, an d b e lo w , usin g a m u l t i l a y er b o ar d (s e e f i gur e 47). th e so t - 23-5 p a c k a g e p r esen ts a c h al len g e in k e ep in g t h e lea k a g e p a t h s t o a minim u m. t h e p i n s p acin g is v e r y t i gh t, so extra ca r e m u s t be u s ed wh e n c o n s tru c ti n g th e g u a r d ri n g ( s ee f i g u r e 4 8 f o r r e co mmen de d guar d-r i n g co n s t r uc t i o n ). f i gure 4 6 . c u rr ent l i mi ti ng res i st or cap a citiv e load driv e c a p a c i ti v e l o a d i n tr o d u c e s a po l e i n th e a m p l i f i e r l o o p r e s p o n se d u e t o t h e f i ni t e o u t p u t im p e da nce o f t h e a m p l if ier . this ca n ca use ex ces s i v e p e a k in g a n d r i n g in g in t h e r e s p o n s e . th e AD8067 wi t h a ga in o f +10 wi l l ha n d le u p to a 30 pf ca p a ci t i v e load wi t h o u t a n excessiv e amo u n t o f p e a k ing (s e e f i gu r e 8). i f g r e a ter ca p a ci t i v e load dr i v e is r e q u ir e d , co n s ider in s e r t in g a s m al l r e sis t o r in s e r i es w i th th e l o a d ( 2 4 . 9 ? is a g o od va l u e to s t a r t wi t h ). c a paci t i v e load dr i v e ca p a b i li ty als o in cr e a s e s as th e gain o f t h e am plif ier in cr e a ses. non-inverting guard ring inverting guard ring f i gure 4 7 . gua r d-r ing c o nfi g u r a t i o ns v in in v v out AD8067 noninverting v i n in v v ou t AD8067 inverting f i gure 4 8 . gua r d-r ing la y o ut s o t - 23 - 5
AD8067 rev. 0 | page 19 of 24 grounding to minimize parasitic inductances and ground loops in high speed, densely populated boards, a ground plane layer is critical. understanding where the current flows in a circuit is critical in the implementation of high speed circuit design. the length of the current path is directly proportional to the magnitude of the parasitic inductances and thus the high frequency impedance of the path. fast current changes in an inductive ground return will create unwanted noise and ringing. the length of the high frequency bypass capacitor leads is critical. a parasitic inductance in the bypass grounding will work against the low impedance created by the bypass capacitor. because load currents flow from supplies as well as ground, the load should be placed at the same physical location as the bypass capacitor ground. for large values of capacitors, which are intended to be effective at lower frequencies, the current return path length is less critical. power supply bypassing power supply pins are actually inputs and care must be taken to provide a clean, low noise dc voltage source to these inputs. the bypass capacitors have two functions: 1. provide a low impedance path for unwanted frequencies from the supply inputs to ground, thereby reducing the effect of noise on the supply lines 2. provide localized charge storage?this is usually accomplished with larger electrolytic capacitors decoupling methods are designed to minimize the bypassing impedance at all frequencies. this can be accomplished with a combination of capacitors in parallel to ground. good quality ceramic chip capacitors (x7r or npo) should be used and always kept as close to the amplifier package as possible. a parallel combination of a 0.1 f ceramic and a 10 f electrolytic, covers a wide range of rejection for unwanted noise. the 10 f capacitor is less critical for high frequency bypassing, and in most cases, one per supply line is sufficient.
AD8067 rev. 0 | page 20 of 24 applications wideband photodiode preamp + v out v b c f + c s c d c m c m r f AD8067 r sh = 10 11 ? f i g u re 49. wideb a n d p h ot odi o de p r ea mp f i gur e 49 s h o w s a n i/v co n v er ter wi t h a n ele c tr ical m o del o f a pho t o d i o de. th e b a sic t r a n sf er fun c t i o n is: f f f photo out r sc r i v + = 1 w h er e i pho t o is th e o u t p u t cur r en t o f t h e p h o t odio de , a n d t h e p a ra lle l co m b ina t io n o f r f an d c f s e ts t h e sig n a l ba n d wid t h. t h e s t a b l e b a n d w i d t h a t ta i n a b l e w i th th i s p r ea m p i s a fu n c ti o n o f r f , th e g a i n ba n d w i d t h p r o d u c t o f th e a m p l i f i e r , a n d th e t o tal ca p a ci t a n c e a t t h e am plif ier s s u mmin g j u n c t i o n , i n c l udin g c s and t h e am plif i e r in p u t ca p a ci t a n c e. r f a n d th e t o tal c a pa c i ta n c e p r od uce a p o le i n t h e a m plif i e r s loo p t r a n smis sio n t h a t ca n r e s u l t in p e a k in g an d in s t ab i l i t y . a ddin g c f cr e a tes a zer o in t h e lo o p t r a n smis sio n t h a t co m p en s a tes f o r t h e p o le s ef f e ct a n d r e d u ces t h e s i gn al b a n d wi d t h . i t c a n be s h o w n th a t th e s i gn al ba n d wi d t h r e s u l t in g in a 45 phas e ma rg in ( f (45) ) is def i n e d b y t h e exp r es sio n : () s f 45 c r gbp f = 2 gbp is t h e uni t g a in b a n d wid t h p r od uct, r f is th e f eed ba c k r e s i st ance, and c s i s th e t o tal c a pa c i ta n c e a t th e a m p l i f i e r s u m m i n g ju n c t i on ( a mp l i f i e r + p h ot o d i o d e + b o a r d p a r a s i t i c s ) . th e va l u e o f c f tha t p r od uces f (45) can be s h o w n t o be: gbp r c c f s f = 2 th e f r e q uen c y r e s p o n s e in t h is ca s e wi l l s h o w a b o u t 2 db o f p e a k in g an d 15 % o v ers h o o t. d o ub lin g c f an d c u t t in g t h e b a n d wid t h in ha l f wi l l r e s u l t in a f l a t f r e q uen c y r e s p o n s e , wi t h a b o u t 5% t r a n sie n t o v er s h o o t. th e p r ea m p s o u t p u t n o ise o v er f r e q uen c y is s h o w n in f i gur e 50. contributor e x p r e s s i o n rms noise (v ) 1 r f 2 57 1 2 4 2 . f r kt f 152 amp to f 1 1 f v noise 4.3 amp (f2C f1) ( ) 1 2 2 f C f c c c c c v f d f m s noise + + + 96 amp (past f2) ( ) 57 1 3 2 . + + + f c c c c c v f d f m s noise 684 rss t o t a l 7 0 8 t a bl e 2 . r m s n o is e cont r i but i o n s of phot odi o de pr e a mp 1 rms n o is e wi t h r f = 50 k?, c s = 0.67 pf , c f = 0.3 3 pf , c m = 1.5 pf , a n d c d = 2.5 pf . frequenc hz voltage noise nv/ hz rf noise f 1 noise due to amplifier ven f 2 1 2 f i g u re 50. phot od i o de v o lt ag e n o is e cont r i but i o n s f i gur e 51 s h o w s t h e AD8067 co nf igur e d as a t r a n si m p e d a n ce ph o t odi o de am plif ier . th e am plif ier is us e d in co n j un ct io n wi t h a jds u n i p has e ph o t odiode dete cto r . this am plif ier has a b a n d wid t h o f 9.6 mh z as sho w n in f i gur e 52 a n d is v e r i f i e d b y t h e desig n e q u a t i on s s h ow n i n f i g u r e 5 0 .
AD8067 rev. 0 | page 21 of 24 AD8067 0.1 ? ? ? using the AD8067 at gains of less than 8 a co mmo n t e c h niq u e use d t o s t a b ilize de co m p en sa t e d a m p l if ie r s i s to in cr e a s e t h e n o is e gain, in dep e n d en t o f t h e sig n a l gain. th e AD8067 ca n b e us e d f o r sig n a l g a in s o f les s t h a n 8, p r o v ide d t h a t p r o p er ca r e is t a k e n t o en s u r e t h a t t h e n o ise ga in o f t h e a m p l if ier is set t o a t leas t th e r e co mm en de d minim u m sign a l ga in o f 8 (s e e f i gur e 54). th e sign a l a n d n o ise ga in e q ua t i o n s f o r a no nin v er t i n g a m p l if i e r ar e sho w n b e l o w . 1 3 1 r r gain signal + = 1 3 1 r r gain noise + = f i g u re 51. phot od i o de pr e a mpl i f i e r t e s t da t a f o r t h e p r e a m p is s h o w n in f i gur e 52 an d f i gur e 53. t h e a d d i t i on of r e s i s t or r 2 m o dif i es t h e n o ise ga in e q ua t i o n , as s h o w n b e lo w . n o te t h e sig n a l ga in e q ua t i o n has n o t c h a n g e d . frequenc mhz transimpedance gain db 100 65 70 75 80 85 90 95 60 0.01 0.1 1 1 0 100 2 1 3 1 r || r r gain noise + = AD8067 c2 0.1 ? ? ? ? f i g u re 52. phot od i o de pr e a mpl i f i e r f r equenc y r e s p ons e f i g u re 54. g a in of l e s s t h an 2 s c he m a t i c m 50ns ch1 830mv ch1 500mv c1 rise 31.2ns c1 fall 31.6ns t this te c h niq u e al lo ws t h e d e sig n er to us e t h e ad8 067 in ga in co nf igura t io n s o f les s tha n 8. th e dra w b a c k to t h i s typ e o f c o m p e n sa ti o n i s th a t th e in p u t n o ise a n d o f fset v o l t a g es a r e also a m p l if ie d b y t h e va l u e o f t h e n o is e ga in. i n addi t i o n , t h e dis t o r t i o n p e r f o r ma n c e wil l be degrade d . t o a v o i d ex ces s i v e o v er s h o o t a n d r i n g in g w h en d r i v in g a ca p a ci t i v e load , t h e ad806 7 s h o u ld b e b u f f e r e d b y a sma l l s e r i e s res i sto r ; i n t h i s ca s e , a 5 1 re si sto r was use d . f i g u re 53. phot od i o de pr e a mpl i f i e r p u ls e r e s p ons e
AD8067 rev. 0 | page 22 of 24 m 50ns ch1 288mv ch1 200mv ch2 200mv t v in v out ref e r e n c e n etw o r k: () 2 3 2 2 1 3 c r || r bandwidth db v ref = ? + resis t o r s r4 an d r1 s et t h e gain, i n t h is cas e an in v e r t in g gain o f 10 was s e le cte d . i n t h is a p plica t io n, t h e in p u t an d o u t p u t b a n d wid t h s w e r e set f o r a p p r o x ima t e l y 10 h z . th e r e f e r e n c e n etw o r k was set f o r a t e nt h of t h e i n p u t a n d ou t p u t b a n d w i dt h , at ap p r ox i m at e l y 1 hz . AD8067 c4 0.1 ? ? ? ? ? f i g u re 55. g a in of 2 p u ls e r e s p ons e single-s upply op er ation th e AD8067 is w e l l s u i t e d f o r lo w v o l t a g e sin g le-s u p pl y a p plica t io n s , g i v e n i t s n- c h ann e l j f et in p u t s t ag e an d rai l -to-rai l o u t p u t s t ag e. i t is f u l l y s p e c if ie d f o r 5 v s u p p lies. s u cces s f u l sin g le- s u p p ly a p plica t io n s r e q u ir e a t ten t i o n to k e ep sig n a l v o l t ag es wi t h in t h e i n p u t a n d ou t p u t h e a d r o om l i m i t s of t h e a m p l i f i e r . t h e i n p u t s t a g e h e adr o o m exten d s to 1.7 v (minim u m ) o n a 5 v s u p p l y . th e cen t er o f t h e in p u t ra n g e is 0.85 v . th e o u t p u t sa t u ra t i o n limi t d e f i n e s t h e h a r d l i m i t of t h e ou t p u t h e a d r o om . t h i s l i m i t d e p e n d s o n t h e amo u n t o f cur r en t t h e am plif ier is s o ur cin g o r sin k in g, as s h o w n in f i gur e 29. f i gure 56. sing le-s up ply o p er at ion s c hematic high g a in, high b a n d width co mposit e amplifier t r adi t io na l l y , an o f fs et v o l t ag e is i n t r od uce d in t h e in p u t n e two r k r e p l acin g gr o u n d as a r e f e r e n c e . this a l lo ws t h e o u t p u t t o swin g a b o u t a dc r e f e r e n c e p o in t, typ i ca l l y mids u p p l y . a t t e n t io n t o t h e r e q u ir e d h e adr o o m o f t h e am plif ier is im p o r t an t, in t h is cas e t h e r e q u ir e d h e adr o o m f r o m t h e p o si t i v e s u p p l y is 3 v ; t h er ef o r e 1.5 v was s e le cte d as a r e f e r e n c e, w h ic h a l lo ws f o r a 100 mv sig n a l a t t h e in p u t. f i gur e 56 s h o w s t h e AD8067 co nf igur e d f o r 5 v s u p p l y o p era t io n wi t h a r e f e r e n c e v o l t a g e o f 1.5 v . c a p a ci t o r s c1 a n d c5 ac-co u p l e t h e signa l in t o a n o u t o f t h e a m p l if i e r a n d p a r t ia l l y det e r m in e t h e ba n d wid t h o f t h e in p u t a n d o u t p u t s t r u ct ur es. th e co m p os i t e am plif ier t a k e s ad van t ag e o f co mb inin g k e y p a r a m e t e r s tha t ma y o t h e r w ise be m u t u a l l y ex c l u s i v e o f a co n v en t i o n a l sin g le am plif i e r . f o r exam p l e, mos t p r e c isio n am plif iers ha v e g o od dc c h aracteris t ics b u t lac k hi g h s p e e d ac c h aracter i s t ics. c o m p osi t e am plif iers co mb in e t h e b e s t o f b o t h a m p l if ie r s t o ac hie v e s u p e r i o r p e rf o r ma n c e o v er th eir sin g le o p a m p co un ter p a r ts. th e AD8067 a n d t h e ad8009 a r e w e l l s u i t e d f o r a co m p osi t e am plif ier cir c ui t, co mb inin g dc p r e c isio n w i t h hig h gain an d b a n d wid t h. th e cir c ui t r u n s o f f a 5 v p o w e r s u p p l y a t ap p r ox i m at e l y 2 0 m a of bi a s c u r r e n t . w i t h a g a i n of ap p r ox i m at e l y 40 db , t h e co m p osi t e am plif ier o f f e rs <1 pa in p u t cur r en t, a gain b a n d wid t h p r od uct o f 6.1 gh z, an d a s l e w ra te o f 630 v/s e c . 1 1 2 1 3 c r bandwidth db C v input = 5 2 1 3 c r bandwidth db C v l output = resis t o r s r2 an d r3 s e t a 1.5 v o u t p u t b i as p o i n t f o r t h e o u t p u t sig n a l to swin g a b o u t. i t is cr i t ica l to ha v e ade q ua t e b y p a s s in g to p r o v ide a g o od a c gr o u n d fo r t h e r e f e r e n c e v o l t a g e. gen e ra l l y t h e b a ndw i d t h o f t h e re fe r e nce ne t w o r k ( r 2 , r 3 , and c 2 ) i s s e l e c t e d to be o n e t e n t h t h a t o f t h e in p u t ba n d wid t h. this en s u r e s t h a t a n y fr eq u e n c i e s be l o w th e i n p u t ba n d w i d t h d o n o t pa s s th r o u g h th e r e f e r e n c e n e two r k in to t h e am plif ier .
AD8067 rev. 0 | page 23 of 24 AD8067 c2 0.1 ? ? ? ? ? m 25ns ch1 0v ch1 1v t c1 ampl 4v f i gure 5 9 . la r g e s i gna l r e sp o n se f i gur e 5 7 . ad80 67 /ad8 00 9 c o m p o s i t e a m pli f i e r a v = 1 0 0 , gbw p = 6. 1 g h z m 25ns ch1 0v c1 ampl 480mv ch1 200mv t th e co m p os i t e a m plif ier is set f o r a ga in o f 100. th e o v era l l ga in is se t b y th e f o ll o w i n g eq u a ti o n : 1 1 2 + = r r v v i o th e o u t p u t s t a g e is s e t f o r a ga in o f +10; t h er ef o r e, t h e AD8067 has a n ef f e ct i v e ga in o f +10, t h er eb y al lo win g i t t o a ma in t a in b a n d wid t h in ex ces s o f 55 mh z . th e cir c ui t ca n b e t a ilo r e d f o r dif f er en t g a in va l u es ; k e ep in g t h e r a ti o s r o u g hl y th e sa m e w i ll e n s u r e t h a t th e ba n d w i d t h i n t e gri t y i s main t a in e d . d e pen d in g o n t h e b o ar d la yo u t , ca p a ci to r c5 ma y b e re qu i r e d t o re du c e r i ng i n g o n t h e o u tput . t h e g a i n b a ndw i dt h a n d p u ls e r e s p o n s e s a r e s h o w n in f i g u r e 58, f i gur e 59, a n d f i gur e 60. f i gure 6 0 . smal l s i gna l r e sp o n se l a y o ut o f t h i s c i rc u i t re qu i r e s a t t e n t i o n t o t h e ro ut i n g a n d l e ng t h o f t h e f e e d b a c k p a th. i t s h o u ld b e k e p t as s h o r t as p o s s i b le to minimize s t ra y ca p a ci t a n c e . frequenc mhz db 44 24 26 28 30 32 34 36 38 40 42 0.1 1 1 0 100 f i gure 58. g a in b a ndwidth response
AD8067 rev. 0 | page 24 of 24 outline dimensions 0. 3 0 compliant to jedec standards mo-178aa pin 1 1. 6 0 bs c 2. 80 bs c 1. 9 0 bs c 0. 95 bs c 1 3 4 5 2 0. 2 2 0. 0 8 0. 6 0 0. 4 5 10 f i gure 61. 5-l e ad p l astic su r f ace m o un t p a ck ag e [so t -2 3} (r t - 5) di me nsio ns sho w n i n mi ll im e t e r s esd caution esd (ele ctrostati c discharge) sensitive device. elect r osta tic charges as high as 4000 v readily accumulate on the human body and test equipment and can discharge without detec t i o n. al though this produc t features proprietary esd protec tion c i rc uitry, permanent damage may oc c u r on de vices subjected to hig h energy ele c tros tatic discharges. therefore, prope r esd precautio n s are recommended to av oid performance degradation or loss of functiona l ity. ordering guide model temper ature ra nge packa g e desc ri ption packa g e outlin e branding infor m ation ad8 067 art-r e e l C40c to + 85c 5-lead so t- 23 rt-5 hab ad8 067 art-r e e l 7 C40c to + 85c 5-lead so t- 23 rt-5 hab ad8 067 art-r 2 C40c to + 85c 5-lead so t- 23 rt-5 hab t a bl e 3 . o r d e r i ng g u ide ? 2002 anal og de vices, inc. all ri ghts rese rved. tra d emarks a n d registered tra d ema r ks are the proper ty of th eir respectiv e co mpan ies. printed in the u. s.a. c03205-0-11/02(0)

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