Systematic Design of Fully Balanced Differential Current- Mode Multiple-Loop Feedback Filters Using CFBCCII

Transcription

1 RDOENGNEERNG, VOL. 9, NO., PRL 85 ystematc Desgn of Fully Balanced Dfferental urrent ode ultpleloop Feedback Flters Usng FB Wang hunhua, Leng Yang, Zhang Qujng, Fe Yu chool of omputer and ommuncatons, Hunan Unversty, hangsha, 8, hna bstract. n ths paper, a systematc desgn method producng balanced currentmode flters s proposed, usng current controlled fully balanced secondgeneraton current conveyor crcut (FB). n ths method, many knd of allpole multple loop feedback (F) current mode balanced flters can be obtaned, all the produced flters have fully balance structures. oreover, the frequency of the flters can be electroncally adjustable. The produced nthorder flters are constructed by n FBs and n grounded capactors, no resstors are needed. The senstvtes of the flters and nfluences of FB parastc elements on flters are analyed. Keywords Fully balanced, current mode, flter, current conveyor, multpleloop feedback formattng.. ntroducton ctve flters stand very mportant postons n many areas such as hghspeed computer communcaton transcever chps, retreval and storage systems, rado and TV recevers, and analog nterface systems n general, numerous secondorder [] and hghorder flters have been reported [9]. There are bascally three approaches to the desgn of actve flters wth a hgh order: the cascade of bquadratc sectons; smulaton based on passve L ladder prototypes; the multple loop feedback (F). ompared wth cascade structures whch have hgh senstvty and ladder topologes that can mplement only magnary axs ero, F actve flters have both low senstvty and arbtrary transmsson eros. n addton, F flters have smple structure, so the multple loop feedback s a very mportant approach to desgn nthorder flters []. ystematc desgns of flters are very mportant, t can produce multple structures. Tll now some knds of systematc desgns of F nthorder flters have been proposed. For example, papers [58] proposed systematc desgns of nthorder F flters based on OT (Operatonal Transconductance mplfer). However, they belong to voltage mode flters, and have relatve complex structures. n addton, all these crcuts but the one n paper [5] have not fully balanced structure. Paper [9] proposed current mode nthorder F flters based on OT, but t has not fully balanced structure, too. urrentmode crcuts have obvous advantage by comparson wth voltagemode crcuts, currentmode crcuts have low mpedance, they have hgh speed and large bandwdth, lower nonlnear dstorton and wder dynamc range, and the power consumpton s low. fully balanced flter can suppress even order dstorton and commonmode nterference effectvely. t has an mportant applcaton n communcaton systems. n lterature [5], systematc desgns of fully balanced flters were proposed. However, t belongs to voltage mode crcut, too, n OT and n capactors are requred to mplement nth order flter. oreover, the system s mplemented by OT that has narrow dynamc range and worse lnearty compared wth second generaton current conveyor ()., as a basc buldng block n the currentmode sgnal processng, s wdely used n flter desgn, ether sngleended [5] or dfferental [6]. ompared wth sngleended crcuts, dfferental current mode crcuts have the ablty of reducng even harmoncs as well as commonmode nterference, thus they play an mportant part n telecommuncatons. n a prevous work, hu et al. proposed a dfferental dfference current conveyor (DD) and a secondorder flter whch can reale lowpass and bandpass flterng functon [7]. n 997, Elwan et al. proposed two new dfferental voltage current conveyors (DV) [8], and realed a contnuoustme current mode OFET flter. fully dfferental current conveyor (FD) [9] was presented by Edawy. The crcut employs fully dfferental structure and suppresses undesrable common mode sgnals. new realaton of FD was proposed by olman [], and the termnals X, Y and Z of ths crcut are all dfferental. n modern VL applcatons, balancedmode structures are ncreasngly used. n a balanced crcut, output commonmode sgnal s kept constant, and t s entrely ndependent of the nput sgnal. Therefore, performance of a fully balanced structure (such as dynamc range, nose suppresson, and harmonc dstorton) can be largely mproved. fully balanced current conveyor [] provdes a par of dfferental Y termnals and a par of dfferental X termnals. The crcut ntroduces a commonmode feedback

2 86 H. WNG ET L., YTET DEGN OF FULLY BLNED DFFERENTL URRENTODE ULTPLELOOP crcut and an R compensaton crcut whch keeps the common mode sgnal constant, whle ncreasng the dynamc range of dfferental mode sgnals. n, laher ntroduced a O fully dfferental current conveyor []. However, n all of these prevously reported elements, there exsts a relatvely sgnfcant voltage trackng error from termnal Y to termnal X. The parastc resstor n termnal X leads to transfer functon error n ther applcaton crcuts. oreover, these elements lack electronc programmablty, whch has become a key feature n recent applcaton. n ths paper, by ntroducng a new element, current controlled fully balanced secondgeneraton current conveyor crcut (FB), a systematc desgn method producng allpole F currentmode flter s proposed. The FB wth fully balanced structure can suppress commonmode sgnals, and ts port relaton has electronc programmablty. The produced flters from systematc method have fully balanced structure whch can reduce even order dstorton and commonmode nterference effectvely. oreover, the frequency of the flters s electroncally adjustable. The senstvty of the flter s less than. n addton, the structure of the crcut s smple, all the nthorder flters are constructed by n FB, n capactors and no resstors. ll capactors are grounded, so the crcut s convenent for ntegraton.. FB rcut and Realaton The crcut symbol of FB s shown n Fg., where denotes the bas current of FB. Here, Y +, Y are dfferental voltage nput termnals, X + and X behave as dfferental voltage trackng termnals, Z +, Z + and Z, Z are the current output termnals. The number of current output termnals Z can be extended f necessary. ts deal port characterstcs can be expressed as: Y Y VX VX ( VY VY) ( X X ) R () X Z Z Z Z X X where R x represents the parastc resstance of termnal X. V Y+ Y+ Y + X+ Fg.. ymbol of FB. FB V Y Y Y X+ X The crcut frame dagram of FB s gven n Fg.. The crcut s made up of four blocks: the dfferental voltage nput stage, the secondgeneraton current controlled current conveyor (), voltagesamplng crcut, and the common mode feedback crcut (FB).The basc prncple of the crcut s analyed as follows: There are two sgnalfeed paths n the crcut, the feedforward and the Z + Z Z + Z X + + feedback path. The feedforward path conssts of a dfferental nput stage and two s. Dfferental voltage sgnals are added to the dfferental nput stage, and the voltages would be transferred to the ponts and B. The current controlled current conveyors () are employed to transfer V and V B to the output termnals. The feedback path conssts of voltage samplng crcut and FB crcut. The voltages of the ponts and B wll be sampled n the voltage samplng block, where the commonmode () voltage V s generated. The FB crcut s employed to suppress the sgnals, by comparng V and V R, V s forced to follow V = V R, n ths way, the sgnal can be effectvely suppressed. Fg.. Frame dagram of FB. The realaton of the FB crcut s llustrated n Fg., ~ consttute two pars of dfferental nputs, the parameters of the transstors are symmetrc. The crcut has hgh nput mpedance as the nput voltages are appled to the crcut by the gates of O transstors, so Y+ = Y =. ssumng that all transstors operate n ther saturaton regon, and channellength modulaton effects are not taken nto consderaton, we get: ( KW / L)( VG VT ), () W L.5 K cox, KT () where K s the transconductance parameter, W and L are the wdth and length of the dran channel respectvely, V T s the threshold voltage. The two pars of dfferental transstors are loaded by ~ whch carry equal bas currents ( ). ~ compose current mrrors. o:, () B (5) where Ι Μ (=) respectvely denotes the dran current of the transstor. From (), (5), we get:. (6), f channel dmensons of ~ are: W /L =W /L, W /L =W /L, we get: ( V ( V Y Y FB V Y+ Y + Dfferental nput tage V Y Y V V V R V V ) / V T T Voltage amplng D V ) / V Y B V B V X + Z + Z + B X + V Y V Z + G V V x+ Z+ Z x+ Z+ Z (7)

3 RDOENGNEERNG, VOL. 9, NO., PRL 87 V DD Z+ Z X + X c7 5 9 Y+Y B c X Z X Z Z V R 5 c5 V c c R R c c V B V Fg.. Then the expressons for V and V B become: V ( ) VB VY V. (8) Y 5 ~, ~ consttute two O translnear loops, 5 ~ transfer the voltage from pont to X+, and ~ transfer the voltage from pont B to X. Now consder the translnear loop of 5 ~ : 5 and, 6 and, 7 and, 8 and 9 consttute four compound transstors respectvely. f the channel aspect ratos W/L of NO transstors n the four compound transstors are dentcal, and the ratos W/L of PO transstors are alke (all transstors operate n saturaton regon), we can get []: X ( eff B) eff n p /( n p ) R K K K K K K where K n and K p are the transconductance coeffcent of the PO and NO transstor, so R x can be adjusted by. From () and (9), R x s ncreased whle temperature ncreases. n Fg., ~ 6, 7 ~ 9, 9 ~ 5, 5 ~ 5 are four current mrrors respectvely, then Z+ = Z+ = x+, Z = Z = x, so: Z Z X X rcut realaton of FB. (9). () t s clear that the proposed FB satsfes the characterstcs shown n (). n Fg., the common mode feedback crcut conssts of 8 n addton to two resstors (R) and two capactors (). The operaton of the FB s explaned n [] n detal. The FB crcut suppresses the commonmode and ncreases the nput dynamc range to a great extent, and t can suppress commonmode nterference effectvely. FB s smulated n PE usng.5µm O process parameters for transstors shown n Tab.. The dmensons of O transstors are lsted n Tab.. upply voltages are.65 V..model ENO nmos (level= UO=6.5 TOX=.E8 TPG= VTO=.6 J=.8E6 +XJ=.5E6 R=7 RH=.7 LD=.E6 ET= VX=E NUB=.7E7 PB=.76 +PH=.95 THET=.9 G=.69 KPP=. F= WD=.E6 J=76.E5 +J=.57 JW=5.68E JW=. GO=.8E GDO=.8E +GBO=.5E KF=.7E8 DELT=. NF=.E).model EPO pmos (level= UO= TOX=.E8 TPG= VTO=.58 J=.8E6 +XJ=.E6 R=886 RH=.8 LD=.E6 ET= VX=E NUB=.8E7 PB=.9 +PH=.95 THET=. G=.76 KPP= F= WD=.E6 J=85E5 +J=.9 JW=.67E JW=.6 GO=.8E GDO=.8E +GBO=.5E KF=.8E9 DELT=.8 NF=.5E) Tab...5µm O process parameters for transstors. O Transstors W/L (µm) Transstos W/L(µm), /.5 5 6/.5, 8/.5 5 8/ /.5 /.5, / /.5 8/.5 9, 7 7 9, 5 5 /.5 /.5 c c /.5 c5 c7 /.5 Tab.. Dmensons of O transstors n FB. The theoretcal result and the smulated result of relatonshp between R x and are gven n Fg.. Fg.. mulated relatonshp between R x and.

4 88 H. WNG ET L., YTET DEGN OF FULLY BLNED DFFERENTL URRENTODE ULTPLELOOP The relaton of R x and temperature has been gven n Fg. 5. From Fg. 5, t can be seen that the nfluence of temperature on R x s very small. Fg. 5. The nfluence of temperature on R x of FB. The transconductance commonmode gan ( ) s ( + + )/(V y+ +V y ). The smulaton result of of FB s gven n Fg. 6. t can be seen from Fg. 6 that t s equal to.7 6 whch s very small. The nput and output mpedance of FB can be seen n Fg. 7 and Fg. 8 whle bas currents are equal to, 5, 65 μ respectvely. t s clear that nput mpedance s ndependent of bas currents, but output mpedance s nfluenced by bas currents. From Fg. 7, t s known that the nput mpedance s larger than 6 and.5 when frequency s less than H and H respectvely. From Fg. 8, t s known that output mpedance s equal to approxmately when frequency s less than H. (emens ) nput mpedance (Ω). Fg. 6. ommonmode gan of FB. T.G. K..T = =,5,65μ The stablty of FB s analyed. From Fg., t s clear that the stablty of FB s determned by the crcut between X and Y where the feedback crcut exst n. ccordng to [7], the stablty crtera are as follows: at the frequency (f c ) wth transfer gan = db, f 8 o < phase < 8 o and phase margn (phase shft dstance from ±8 ) > 5, the system s stable. The gan and phase of dfferental termnal X and Y transfer functon (V x+ V x )/(V y+ V y ) wth three bas currents are shown n Fg. 9. t can be seen that at about f c =.8 GH, gan s db and phase margn > 5. o the system satsfes stablty crtera and s stable. The dfferental currents of termnal Z and X wth three bas currents: μ, 65 μ and μ are gven n Fg.. Fg. shows the smulated D characterstc of dfferental voltages between termnal X and Y, the voltage of X termnals s undstorted when the nput voltage of Y termnals s.5 V. o the nput dynamc range s.5 V. (Vx+ Vx) / (Vy+ Vy) Fg. 9. The gan and phase response of dfferental voltage transfer between X and Y n FB. (+ Z) / (x+ x) Fg.. mulated frequency response of ZX current..5 =u =65u =u =u =65u =u =µ =65µ ((Vx+ Vx) / (Vy+ Vyphase((Vx+ Vx) / (Vy+ Vy)) Frequency (H ) 6 8 Phase((Vx+ Vx) / (Vy+ Vy))( ) Fg. 7. nput mpedance of Y termnal of FB..5 V x+ V x (V).5 =µ Output mpedance (Ω)..5 =u =5u =65u Frequency(H) Fg. 8. Output mpedance of FB. V Y+ V Y (V) Fg.. mulated YX D characterstcs. From above analyss, t s clear that the FB wth fully balanced structure can suppress commonmode sgnals, and ts port relaton has electronc programmablty compared wth classcal fully dfferental operatonal amplfers [7].

5 RDOENGNEERNG, VOL. 9, NO., PRL 89. ystematc Desgn ethod of Fully Balanced urrent ode Flter. FBased ntegrator + Y+ X+ X Y FB Z+ Z (a) tructure (b) ymbol Fg.. tructure and symbol of FB ntegrator. The structure of FB ntegrator s shown n Fg.. (a). Routne analyss based on (), we can get: o o X X ( ) ( ) R s X X X. () The symbol of FB ntegrator s show n Fg.. (b), form () we can get: o o H() s sr s. () X. odel and Relatons of the F Balanced urrent ode Flter The model crcut of F balanced current mode flter based on FB s shown n Fg.. The crcut s constructed by two parts: The feedforward crcut consstng of n FB ntegrators and the feedback network constructed symmetrcally by lnks connectng f, f +, oj + and oj. From Fg., the feedback equatons can be obtaned as follows: F, F () f o f o Fg.. odel crcut of dfferental F flters o + o Feedback network F f /(sτ ) /(sτ ) Feedback network F f where o + = [ o +, o +... on + ] T, o = [ o, o... on ] T s the output vector, and f + = [ f +, f +... fn + ] T, f = [ f, f... fn ] T s the feedback vector. F= [f j ] n n s the feedback matrx, when <j, f j =, so F s an upper trangular matrx, namely: /(sτ) oj + (,j=,, n; j) /(sτ n ) oj (,j=,, n; j) + o + o f f f f f f f F f f f n n n nn () Based on the model crcut n Fg. and (), the equatons can be derved: ( ) ( ) (5) n n f f o o where n n,,, T, and s s. s s n From () and (5), the transfer functon of systematc model crcut n Fg. can be shown as followng: o o H() s (6) F ( s) n where (s) represents the determnant of (s). n. Flter Producton and ynthess To llustrate the general desgn theory above, we take the desgn of fourthorder flter as an example. The system matrx (s) of the flter s: s f f f f s f f f s (). (7) s f f s f From (6) and (7), the transfer functon of the fourorder flter system can be derved: H ( s) ( ) s ( f f f f) s [ ( f f f ) f f ( f f f) f f (8) f f ( f f f )] s [ ( f f f f f f f f ) ( f f f f f ) ( f f f f f ) ( f f f f f f f f)] ( f f f f f f f f f f f f f f f f f f f f ) We can obtan a varety of fourthorder flters by selectng dfferent f j, and we wll show four knds of them arbtrarly.

6 9 H. WNG ET L., YTET DEGN OF FULLY BLNED DFFERENTL URRENTODE ULTPLELOOP tructure : f f =f =f =f =, the correspondng flter crcut s shown n Fg.. (a). ts transfer functon s: Hs () ( ) s s s s. (9) tructure : f f =f =f =f =, the correspondng flter crcut s shown n Fg.. (b). ts transfer functon s: Hs () ( ) s s ( ) s ( ) s. () tructure : f f =f =f =f =, the correspondng flter crcut s shown n Fg.. (c). ts transfer functon s: Hs () ( ) s s ( ) s s. () tructure : f f =f =f =f = the correspondng flter crcut s shown n Fg.. (d). ts transfer functon s: + Hs () ( ) s s s ( ) s. () (a) tructure (FLF) (c) tructure (FLF) (b) tructure (LF) (d) tructure (F) Fg.. Four knds of F flters based on FB. The four structures belong to followtheleaderfeedback (FLF), modfedleapfrog (LF), nverse FLF (FLF) and the mnmumsenstvtyfeedback (F) structure respectvely. The structure of FLF s smple; LF provdes the freedom to optme the flter to meet some requrements; FLF can maxme dynamc range; F has low senstvty [6]. t can be seen from Fg. that the fourthorder flter s constructed by FBs and 8 capactors, and we can get the nthorder flter that s constructed by n FBs and n capactors.. Desgn Examples o+ + o o+ + o s an example, we desgn a fourthorder Butterworth flter. The normaled transfer functon of fourthorder Butterworth flter s: ( s.6 s. s H ( s). ().6 s ) The structure n Fg.. (a) s used to reale the flter. From (9) and (), we can get: τ =.87, τ =.765, o+ o o+ o τ =.66, τ =.6, and τ =R x (=~), s the normaled capactor. ettng R x = kω, then we get =65 μ, =.87 F, = 7.65 F, =.66 F, = 6. F. f cutoff frequency (f c ) s equal to H, accordng (), we can get: =6.9 pf, =.8 pf, =7.9 pf, =5.85 pf. f (,,,). () The smulaton results are gven n Fg. 5. The curve responds to =65 μ, and f c = H. The f c of the proposed F flters can be tuned by of FBs. n order to keep form of fourthorder Butterworth flter shown n (), τ must be nvarant. ccordng to τ =R x (=~), f R x s decreased, would be ncreased. ccordng to (), f keeps nvarant, f c wll be ncreased. ccordng to above tune prncple, when choosng = μ, the R x s equal to. kω, t can be obtaned f c =.8 H; when choosng = μ, R x =.77 kω and f c =.8 H. The smulaton results are shown as and respectvely n Fg. 5. mlarly, the stablty of the flter can be analyed. Fg. 5 and Fg. 6 are gan and phase characterstcs of dfferental current transfer functon ( o+ o )/ ( + ) n structure. t can be seen that n Fg. 5, at f c = H correspondng Gan = db, phase = o whch s more than 8 o and less than 8 o, and phase margn = 8 o whch s more than 5 o. The stablty crtera [7] are satsfed to the flter, and t s stable. The tmedoman response and the lnearty of the flter can be seen n Fg. 7 and 8, when settng = 65 μ and the are kept nvarant. From Fg. 8, t s known that the nput lnear range of the flter s larger than m. lg(( o + o )/( + ))(db) B=65u B=u B=u Fg. 5. Frequency response of the flter of structure. Phase of (o + o )/( + )( ) fc( Phase = o ) (Phase argn=8) Bas current=65 u Fg. 6. Phase response of flter of structure. fc(gan=db)

7 RDOENGNEERNG, VOL. 9, NO., PRL 9 (u) 5 + o+ o H( s) j jn( s) j ( s) s j s ( ). (6) s H s ( s) ( s) j jn j The structure n Fg.. (a) s analyed, and the others are smlar to t. From (6) and (9), we can get: Tme (ms) Fg. 7. Tmedoman response of the flter of structure. ( o+ o )(m) ( + )(m) Fg. 8. Lnearty of the flter of structure. Harmonc Frequency(H) Fourer component Hs () s s s s s, (7) Hs () s s s s s s, (8) Hs () s s s s s s s, (9) Hs () s s s s s s s s () where s=jω. t can be seen n Fg. 9 the senstvtes of τ, τ, τ, τ are very close to each other, and are less than. No. K 8.68 No. K No. K.69 7 No. K No. 5 5K.89 7 No. 6 6K.66 9 No. 7 7K 7. 8 No. 8 8K No. 9 9K Tab.. The even order dstorton of flter. The produced flters from systematc method have fully balanced structure whch can reduce even order dstorton and commonmode nterference effectvely. The even order dstorton analyss wth base frequency kh s gven n Tab. where Fourer components of the frst~9th harmoncs are gven. t s noted that even harmoncs are restraned largely. o the flter can reduce even order dstorton..5 enstvty nalyss To study the senstvty n the proposed flter, τ j are mportant parameters. The defnton of senstvty s: H() s j H () s j Hs () j. (5) ccordng to [], t s known that: Fg. 9. enstvty of the flter of structure..6 nfluence of FB Parastc Elements The nondeal model [5] s shown n Fg.. The real has parastc resstors and capactors from the Y and Z termnals to the ground, and a seral resstor at the nput termnal x. α(s) and β(s) are used to represent the followers of the, respectvely, and they are consdered as here. s a nondeal FB, parastc resstors and capactors of Y (ncludng Y+, Y) termnals and Z (ncludng Z+, Z) termnals are almost the same wth Y termnal and Z termnal of respectvely, and t s assumed that they all equal to R y, y and R, respectvely. Fg.. Nondeal wth ts parastc resstors and capactors.

8 9 H. WNG ET L., YTET DEGN OF FULLY BLNED DFFERENTL URRENTODE ULTPLELOOP To study the nfluence of parastc elements n FB, the structure shown n Fg.. (a) s consdered, and t can be transformed to Fg.. Other structures can be analyed n ths way. We defne G, G, G, G,,,, and as the parastc elements of the termnals of FB n Fg., and G y, G y, G y, G y, y, y, y, y as the parastc elements of the Y termnals of FB respectvely. The seral resstance of the x termnals of FB s consdered as R x. + Z Y+ Z X+ Z+ Y Z+ Z Z Y+ Z X+ Z+ Y Z+ Z Z Y+ Z X+ Z+ Y Z+ Z Z Y+ Z X+ Z+ Y Z+ Z o+ o From (), (), (5), we get: f c f ' f c c c ' c f (,,,) ' c c (6) where f c ' s the cutoff frequency of the flter ncludng the parastc elements of the FBs. To verfy the analyss, we keep = 65 μ nvarant, change the capactors, the smulated results and theoretcal ones (from ()) are gven n Fg.. t can be seen that the smulated curves are n accordance wth theoretcal ones when frequency s less than H. When frequency s larger than H, the capactors (=~) are comparable wth parastc capactors, and nondeal characterstc of FB needs to be consdered, the frequency modfed formula shown n (6) can be used. Fg.. Proposed flter of structure ncludng the parastc elements of the FB. nalyng Fg. yelds followng equatons: y Y j j G G G G y y y y j G y y Y j j G y y j G mlarly, we can get Y, Y. y y y y, (). () Y j j G () where Y =/Z, y = y, =, G y =G y =G y +G (=~ ). t s consdered that y and are smaller than pf, G y s smaller than 6, and the frequency f c s more than H. Therefore, Y, Y, Y, and Y can be approxmated by: Y j j G j y j y y Y j j G y y y G y j G y j y j j (,,) y y y, (). (5) From () (5), t s observed that the parastc capactors are the man nfluence factor, we defne that c ' (=~) as the capactors ncludng the parastc elements of the FBs. Because of y and are smaller than pf, the parastc capactors can be neglgble by comparson f >> ( y + ) (=~), and the FB can be seen as deal one. Fg.. mulaton results of the nfluence of parastc elements to the proposed flter. From above analyss, t can be known that compared wth other crcut [59], the flter suppresses even order dstorton, has wde dynamc range and good lnearty, low senstvty.. oncluson Ths paper proposed a method of desgnng nthorder multloop feedback flter based on FB. The method has followng advantages: The varous current mode balanced structures of the lowpass flters can be generated by changng the form of the feedback; fully balanced structure of the flter can reduce even harmoncs and commonmode sgnals effectvely; the cutoff frequency of the flter can be controlled by the bas current of FB. The produced nthorder flters are constructed by n FBs and n R passve elements; all passve components are grounded, so the flters can be ntegrated convenently; the flters are not affected by nondeal characterstc of FB when frequency s less than H. cknowledgements Ths work s supported by the Natonal Natural cence Foundaton of hna (No. 6676).

9 RDOENGNEERNG, VOL. 9, NO., PRL 9 References [] PPZOGLOU,.., KRYBK,.. Nonnteractng electroncally tunable based currentmode bquadratc flters. EEE Proc G, 997, vol., no., p [] WNG,. H., ZHOU, L. new OT currentmode bquad flter wth sngle nput and multple outputs. nternatonal Journal of Electroncs and ommuncatons, 8, vol. 6, no., p.. [] HNG,.., LHH, B.. ngle fully dfferental current conveyor bquad flters. EEE Proceedngs on rcut, Devce and ystems,, vol. 5, no. 5, p [] LKER, K. R., HUNN, R., GHU,.. ultpleloop feedback topologes for the desgn of lowsenstvty actve flters. EEE Trans. on rcuts and ystems, 979, vol. 6, no., p.. [5] UN, Y., FDLER, K. Fullybalanced structures of contnuoustme LF OT flters. n Proceedngs of 998 EEE nternatonal onference on Electroncs, rcuts and ystems, 998, p [6] UN, Y., FDLER, J. K. tructure generaton and desgn of multple loop feedback OTgrounded capactor flters. EEE Transactons on rcuts and ystems : Fundamental Theory and pplcatons, 997, vol., no., p.. [7] HNGKT, K., HUNGN,., HUN, L., et al. ynthess of optmal OT flter structures wth arbtrary transmsson eros va NLP. n Proceedngs of 8 EEE sa Pacfc onference on rcuts and ystems, 8, p [8] OHED, O.., OLN,.., OLN,.. Hghorder Gm flters wth current transfer functon based on multple loop feedback. n 7 EEE nternatonal onference on gnal Processng and ommuncatons, 7, p [9] UN, Y., FDLER, J. K. urrentmode multpleloop feedback flters usng dual output OTs and grounded capactors. nternatonal Journal of rcut Theory and pplcatons, 997, vol. 5, p [] PPZOGLOU,.., KRYBK,.. Nonnteractng electroncally tunable based currentmode bquadratc flters. EE Proc G, 997, vol., no., p [] UN, Y., HE, Y. ctve flters usng sngle current conveyor. n Proceedngs of the EEE nternatonal onference on Robotcs, ntellgent ystems and gnal Processng,, p.. [] KOKL,., GB,. versatle sgnal flow graph realaton of a general current transfer functon. nt. Journal of Electroncs and ommuncatons, 8, vol. 6, no., p.. [] HUNNG,., OLN,.., WY,. N.. nalytcal synthess of lowsenstvty hghorder voltagemode DD and FDgrounded R and allpass flter structures. EEE Transactons on rcut and ystems: Regular Papers, 7, vol. 5, no.7, p.. [] JREREEORNKUN,., TNGRRT, W., URKPONTORN, W. Tunable ellptc flters usng multoutput current controlled conveyors. n EEE Regon onference TENON,, p. 9. [5] WU J, ERY, E. urrentmode ladder flters usng multple output current conveyors. EEE Proc rcut Devces yst, 996, vol., no., p. 8. [6] H, W.X., HN, Q.Q., WNG, H.Y. Fully dfferental currentmode flter based on DD. n EEE sapacfc onference on rcuts and ystems., p [7] HU, W., LU,.., HEN, J.J. O dfferental dfference current conveyors and ther applcaton. EE Proceedngs G: rcuts Devces and ystems, 996, vol., no., p [8] ELWN, H. O., OLN,.. Novel O dfferental voltage current conveyor. EE ProceedngsG: rcuts, Devces and ystems, 997, vol., no., p. 95. [9] EDWY,., OLN,.., ELWN, H. O. novel fully dfferental current conveyor and applcatons for analog VL. EEE Transactons rcuts and ystems: nalog and Dgtal Processng,, vol. 7, no., p. 6. [] OLN,.. Fully dfferental O based on dfferental dfference transconductor. nalog ntegrated rcut and gnal Processng, 7, vol.5, no., p. 95. [] LZHER, H.., ELWN, H., L,. O fully balanced secondgeneraton current conveyor. EEE Transactons on rcuts and ystems,, vol. 5, no. 6, no [] LZHER, H.. O hghly lnear fully dfferental current conveyor. Electroncs Letters,, vol., no., p. 6. [] WNG,.H., HE, Z.X., LU, H.G. New O currentcontrolled second generaton current conveyors. n Proc. th EEE nternatonal onference on rcuts and ystems for ommuncatons, 8, p. 7. [] WYZYNK,., HUNN, R., ZZEPNK,., et al. Desgn of a.7 GH Lnear OT and a 5 H Ellptc Flter n Bpolar Transstorrray Technology. EEE Transactons on rcuts and ystems Part, 99, vol., no., p. 9. [5] FBRE,., D, O., BRTHELEY, H. On the frequency lmtatons of the crcuts based on second generaton current conveyors. nalogue nt. rc. & gnal Process, 995, vol. 7, no., p. 9. [6] LKER, K. R., HUNN, R., GHU,.. ultpleloop feedback topologes for the desgn of lowsenstvty actve flters. EEE Proceedngs on rcut ystems, 979, vol. 6, no., 979, p.. [7] WLLY,... nalog Desgn Essentals. prnger, 6, p. 56 to 6. bout uthors... Wang hunhua for bography see p. 8. Leng Yang was born n hangde, Hunan, hna, n 98. he receved the B.. from Hunan Normal Unversty n 6. he s studyng n Hunan Unversty for master degree now. he s nterested n analog crcut and flter desgn. Zhang Qujng was born n Jshou, Hunan, hna, n 98. he receved the B.. from chool of omputer and ommuncaton, hangsha Unversty of cence and Technology. he s studyng n Hunan Unversty for doctor degree now. he s nterested n analog crcut and flter desgn. Fe YU was born n nqng, nhu, hna, n 98. He receved the B.c degree from nhu Normal Unversty, nhu, hna, n 7. He s currently a doctor n the chool of omputer and ommuncaton n Hunan Unversty. He focuses on rado frequency ntegrated crcut desgn and UWB communcatons.