Novel Low Voltage CMOS Current Controlled Floating Resistor Using Differential Pair

Transcription

1 48 S. A. TEKİN, H. ERCAN, M. ALÇI, NOVEL LOW VOLTAGE CMOS CURRENT CONTROLLED FLOATING RESISTOR Novel Low Voltage CMOS Curret Cotrolled Floatig Resistor Usig Differetial Pair Sezai Aler TEKİN, Hamdi ERCAN, Mustafa ALÇI Det. of Electrical ad Electroics Egieerig, Erciyes Uiversity, 3839, Kayseri, Turkey Det. of Avioics, Erciyes Uiversity, 3839, Kayseri, Turkey Abstract. I this aer, a low voltage CMOS curret cotrolled floatig resistor which is coveiet for itegrated circuit imlemetatio is desiged by usig differetial air. The roosed resistor has a simle circuit structure ad low ower dissiatio. This circuit is required ±.75 V as a ower suly. The basic advatages of this circuit are wide tuig rage of the resistace value, satisfied frequecy erformace ad worthwhile dyamic rage. As well as the roosed circuit has floatig structure, it is able to be used both ositive ad egative resistor. The erformaces of the roosed circuit are simulated with SPICE to justify the reseted theory. Keywords CMOS active resistor, differetial air, low voltage circuits.. Itroductio It is maily utilized resistor i aalogue electroic circuits. However, owig to obtai resistace i silico chi, it is ecessary to detai large areas i the chi. This situatio is ot aroriate i terms of roductio efficiecy. Also, these resistors, which are geerated i the chi, may ot rovide determied resistace value. Because of these reasos, active resistor circuits are highly imortat for itegrated circuits. It was itroduced may varieties of active resistor ad alicatios i revious studies [-5]. Biolar-based floatig resistor was reseted, such as class AB cotrolled resistor, resistor usig oeratioal tracoductace amlifier (OTA based o biolar trasistor, i the literature [-3]. Although these resistors have good frequecy erformace, the dyamic rage of the circuit is restricted. Furthermore, the resistor circuits iheretly cosume more ower comared with MOS-based active resistors. Active resistor usig MOS trasistors ad its alicatios are itroduced i the revious works [6-]. But this resistor is limited i oit of frequecy resose ad adjustability. O the other had, active resistors usig curret coveyors are reorted as differet resistor desigig techiques [3], [4]. But, these structures have assive comoets as resistor. Moreover, these circuits are icoveiet for itegrated circuits (IC. Tuable active resistors are cotrolled by usig either voltage or curret. Voltage cotrolled resistors (VCR are itroduced i [9-]. VCRs reset good dyamic rage erformace. But, adjustable rage of the VCRs is restricted for geerally utilized gate voltages as a cotrol argumet. Cotrol voltage is limited by suly voltage. Curret cotrolled resistors (CCR rovide facility to tue wide resistace value rage [-4]. This caability of the CCR is a imortat advatage for rogrammable aalog circuit s alicatios. I additioal, it ca be iterreted that CCRs exhibit accetable frequecy erformace. Also, VCRs havig good liearity are reseted i literature [5], [6]. But these roosed circuits require high suly voltage ad have restricted cotrol rage comarig with CCRs. Recetly, low voltage disositio has bee raised o electroic circuits desig. Numerous electroic alicatios emloyig i the low voltage are itroduced i the literature [7], [8]. Circuits usig lower suly voltage allow oeratig i lower ower dissiatio. Low voltage active resistors ad their alicatios are icluded i oly a few studies i the literature [4], []. Floatig gate MOSbased low voltage resistor is reorted i []. But, this resistor is tued by voltage ad adjustable value rage of the resistace is a few kωs. I this aer, floatig active resistor is desiged by utilizig CMOS differetial air. The resistor cosists of oly two differetial airs. Also, the circuit ca be realized easily cosiderig IC. This circuit is able to achieve both egative ad ositive resistace with small modificatio i the circuit. Cotrol argumet is biasig curret for roosed circuit. Hereby, adjustable rage of the resistace value is rather wide. The aer resets CMOS based curret cotrolled floatig resistor oeratig at suly voltage of ±.75 V. Therefore, ower cosumtio of the circuit is at reasoable levels. The roosed circuits have bee simulated usig SPICE i.35 µm CMOS techology. Also, a badass filter is emloyed to demostrate the caability of the roosed resistor.

2 RADIOENGINEERING, VOL., NO., JUNE Proosed Floatig Active Resistor Fig. idicates differetial air as the core of floatig resistor. Assumig that all the trasistors are oerated saturatio regio with their sources coected to the bulk. Drai currets of trasistors M A ad M B ca be writte as, I DA ( / Cox W L VGSA V, (.a I ( / DB Cox W L VGSB V (.b where µ is the electro mobility ad Cox is the oxide caacitace er uit area. I DA ad I DB are the drai currets of trasistors M A ad M B, resectively. I additio, V is the threshold voltage for the NMOS trasistors. Trasistor M C utilizes to reduce imedace value at drai of trasistor M B. Therefore, the differetial air eeds low suly voltage. V i I M B I M A V I M C Fig.. The differetial air structure. V DD -V SS V ad V are two iut voltages alied at the gates as show i Fig.. Iut voltages are described as V V V GSA V GSB ( where V GSA ad V GSB are the gate voltages of trasistors M A ad M B, resectively. Drai curret I DA for trasistor M A is equal to I + i ad drai curret I DB is similar to I. From ( ad (, the differece of iut voltages is give by ( I i I V V. (3 C ( W / L C ( W / L ox If equatio (3 is arraged, curret i will be exressed as i ( V V k 4I k W/L( V V (4 where k =µ C ox is the trascoductace arameter of the NMOS trasistor. I (4, it is 4I >> (/k (W/L (V -V. So, i ca be modified as i ( V V kw/l 4I. (5 ox Equatio (5 shows that i deeds o the biasig curret I. The body effect uo the chael of the NMOS trasistors used i differetial air ca be described usig a modificatio of the threshold voltage, aroximated by the followig equatio, V BS V VO B (6 B where V is the threshold voltage with substrate bias reset, ad V O is the zero-v BS value of threshold voltage, γ is the body effect arameter, ad φ B is the surface iversio otetial of silico ad V BS is the bulk-source voltage. Assume that V BS is zero ad gate bias is sufficiet to isure that a chael is reset, bulk effect ca be eglected for differetial air i Fig. [9]. If both iuts of the MOS differetial air structure are grouded, trasistors M A ad M B are erfectly matched ad curret i would be zero. Practical circuits exhibit mismatch effect betwee the trasistors. For the differetial air show i Fig., the effect of a mismatch i the W/L ratios of M A ad M B, exressed as W L A W W, (7.a L L W W. (7.b L B L Effect of a mismatch ΔV betwee the two threshold voltages are described as V A = V + ΔV ad V B = V. Therefore, offset curret Δi ca be calculated as ( W / L V i I (8.a W / L VGS V where V GS is the gate-source voltage of the M A ad M B. The offset curret is extremely deeded o the biasig curret. Fig. idicates the roosed resistor usig two differetial airs. M ad M 4, M ad M 3 are geerated as differetial airs. All other trasistors act as curret mirror ijected biasig curret I. Usig (5, resistace value of the resistor will be exressed as ( V V R (9 i I k W/L where i = -i, because differetial airs are coected i symmetric. It is obvious that resistace value is easily tued by biasig curret I. Resistace value of the roosed circuit has chage with temerature. PTAT curret geerator as biasig curret of the roosed circuit ca be used for temerature comesatio. It is essetial for ultra-low-ower circuit realizatios [].

3 43 S. A. TEKİN, H. ERCAN, M. ALÇI, NOVEL LOW VOLTAGE CMOS CURRENT CONTROLLED FLOATING RESISTOR V DD M M M M 3 M 4 M 5 I i i V M M 3 V M M 4 M 5 M 6 M 7 M 8 M 9 Fig.. Floatig ositive resistor. -Vss All trasistors of this circuit are aimed to oerate i saturatio regio. M 8 ad M remai i the saturatio regio if the followig coditios are fulfilled: R ( V V. ( i I k W/L ( V DD V ( I i SS V M 8 ( I i M ( I M3 (.a Negative resistace is cotrolled by biasig curret i the same way with the ositive resistor. It is clear that the electroic adjustmet of the resistace is offered by this circuit. Creatig two differet kids of i a sigle circuit is oe of the advatages of the roosed circuit. ( V DD k V SS ( I ( W / L M ( I i M 8 V (.b where k = µ C ox is the trascoductace arameter of PMOS trasistors ad V DD, V SS are suly voltages. I order to remai M i the saturatio regio, the coditio is: ( V DD V V SS ( I i ( I M V M ( I additio, M ad M 4 act as a diode. Also, the defiitios i ( ad ( valid for the other trasistors geerated differetial air. It seems that this resistor circuit ca be oerated i saturatio regio if V DD + Vss > V DS,sat +V where V DS,sat is drai-to-source voltage for all trasistors of the circuits i the saturatio regio. The roosed ositive resistor i Fig. is easily able to be coverted to the egative resistor. A coectio is made betwee the drai of trasistor M ad gates of M 3 istead of M s gate. Additioally, the drai of M 4 is coected to the gate of M istead of M 4 s gate. I this istace, it is clear that i = -i. The defiitio of the egative resistace may be as follows: 3. Simulatio Results The roosed resistor was simulated by SPICE, owig to verify the theoretical aroaches. The SPICE model.35 μm CMOS arameter for NMOS ad PMOS is used i []. The suly voltage is ±.75 V. Asect ratio of the trasistors is give i Tab.. Fig. 3 shows iut differetial voltage versus iut curret of the simulated resistor. i (µa 4uA ua A -ua -4 Trasistor W/L M -M 4 /.7 M 5 -M 5 3/.7 Tab.. Asect ratio of the trasistors. -4uA -5mV -5mV V Vab 5mV 5mV -I(Vab V -V (mv Fig. 3. Curret / voltage characteristic of the roosed circuit.

4 RADIOENGINEERING, VOL., NO., JUNE 3 43 The biasig curret of the resistor is varied from 5 µa to 5 µa ste by ste. It is show that behavior of the resistor is highly liear betwee -5 mv ad +5 mv. The liearity of the roosed resistor deeds o the liear rage of the trascoductace amlifier which cosists of the differetial air. There are some circuit toologies exhibitig liear behavior i literature. But these circuits ca be cotrolled by voltage ad oerate at high suly voltage comarig with our roosed circuit []. Resistace value of the roosed resistor ca be easily tued by biasig curret of the circuit as show i Fig. 3. Frequecy resose of the circuit see i Fig. is show i Fig. 4. The variatio of the resistace magitude with frequecy for a biasig curret of 5 µa ad resistace value of.4 kω is illustrated i Fig values obtaied accordig to differet eak to eak iut voltages are reasoable values. Also, the total ower dissiatio of the roosed circuit is.4 mw. Comariso of the erformace arameters belogig to some circuits ad the roosed circuit is idicated i Tab.. Parameters This study [3] [] [4] Suly voltage ±.75 V ±.5 V ±.75 V ±3 V Iut rage ±5 mv ±5 mv ±3 mv ±5 mv Tuig rage.5kω-mω 5Ω-3kΩ kω-4kω 4kΩ-4MΩ THD Power dissiatio.9% (atmhz.4% (atmhz.8% (at 45 khz.4 mw 6. mw.54 mw - Badwidth.66 GHz 35 MHz - - % Resistace Magitude (db KHz db((v(4 khz KHz V(5 / I(Vab khz.mhz MHz Frequecy MHz MHz.GHz GHz GHz - Frequecy Fig. 4. Frequecy resose of the roosed circuit. The variatio of the total harmoic distortio with eak to eak iut voltage for I = 5 µa ad R =.4 kω is dislayed i Fig. 5. Whe the frequecies were icreased, it was foud that the roosed structure could be oerated with the 3dB badwidth of about.66 GHz. This circuit exhibits a good erformace i terms of the frequecy resose..8 Techology CMOS BJT FGMOS CMOS Negative resistace Yes No No Yes Floatig Yes Yes No Yes Tab.. Comarig of the active resistors erformace arameters. Whe Tab. is ivestigated, it is clear that the roosed circuit has some advatages. If the circuits are comared i terms of suly voltage, the roosed resistor ad the circuit i [] require a small suly voltage. Iut rage ad tuig rage of the roosed circuit are wider tha those of the circuit i []. Although the circuit i [4] has wide tuig rage, it uses high suly voltage cosiderig the roosed circuit. Havig a egative resistace is a imortat advatage for the roosed circuit. Also, frequecy erformace of the roosed resistor is elegat. 4. Badass Filter Alicatio As a alicatio, i order to demostrate the roosed resistor s caability, badass filter is used. Aforemetioed filter structure is see i Fig. 6. % THD.6.4. v i L C Proosed Resistor I v Peak to Peak Iut Voltage (mv Fig. 5. THD % versus iut voltage. The variatio of the THD with iut sigal amlitude for a biasig curret of 5 µa is illustrated i Fig. 5. The THD value is.9 % at 5 mv. It is show that THD Fig. 6. Electroically tuable badass filter. The circuit show i Fig. 6 cosists of a caacitor, iductor ad curret-cotrolled active resistor. The caacitace of the caacitor is.5 F ad iductace value is. mh. The ceter frequecy of the circuit deeds o L ad C values. The ceter frequecy is writte as

5 43 S. A. TEKİN, H. ERCAN, M. ALÇI, NOVEL LOW VOLTAGE CMOS CURRENT CONTROLLED FLOATING RESISTOR w. (3 LC The badwidth (BW of the filter ca be defied as R( I BW (4 L where it is obvious that BW is the fuctio of the roosed resistor. Also, the roosed resistor is defied as R(I i (4. The frequecy resose of the filter is show i Fig. 7. As show i Fig. 7 badwidth of the filter ca be easily adjust with chagig biasig curret of the roosed resistor. v / v i (db - I = µa I = =5 µa I =5 µa - MHz MHz MHz -.MHz MHz MHz db(v(4/v(vab Frequecy Fig. 7. Frequecy resose of the filter. 5. Coclusio I this work, low voltage CMOS based active resistor structure is roosed ad electroically tuable badass filter is tested as a alicatio. The roosed circuit has o assive comoets which are excellet for IC imlemetatios. I additio, the circuit has highly basic structure. The roosed circuit ad badass filter are simulated usig a Sice simulatio rogram ad to cofirm the theory their simulatio results are comared with the theoretical aroaches. The value of the roosed resistace ca be varied from.5 kω to MΩ, with excellet corresodece betwee the theoretical ad simulatio results by chagig the value of cotrol curret I. Also, the roosed circuit is required a low voltage as well as ±.75 V. It is worthy for low ower dissiatio. Resistace of the active resistor ca be obtaied either ositive or egative by usig differet coectio structures as it is idicated i Sectio. Dyamic rage of the resistor is wide as see i Fig. 3. Also, thaks to the wide tuig rage of the resistors, the roosed badass filter ca be alied i a very wide frequecy rage. Fially, such a tuable behavior of the roosed circuit is a attractive feature i geeral electroic circuit desigs ad the circuit is rather coveiet for low voltage IC realizatios of which result i decreasig of ower cosumtio. Refereces [] SENANI, R., SINGH, A., SINGH, V. K. A ew floatig curretcotrolled ositive resistace usig mixed trasliear cells. IEEE Trasactios o Circuits ad Systems II, 4, o. 5, [] KHAN, A., AHMED, M. T. Realisatio of tuable floatig resistors. Electroics Letters, 7th July 986, vol., o. 5, [3] BARTHELEMY, M., FABRE, A. A ew floatig cotrolled resistace oeratig i class AB. IEEE Trasactios o Circuits ad Systems I: Fudametal Theory ad Alicatios,, o. 47, [4] MANOLESCU, A., POPA, C. Low-voltage low-ower imroved liearity CMOS active resistor circuits. Aalog Itegrated Circuits ad Sigal Processig,, vol. 6, o. 3, [5] ERCAN, H., TEKIN, S. A., ALÇI, M. Voltage- ad curretcotrolled high CMRR istrumetatio amlifier usig CMOS curret coveyors. Turkish Joural of Electrical Egieerig & Comuter Scieces,, vol., o. 4, [6] TAJALLI, A., LEBLEBICI, Y., BRAUER, E. J. Imlemetig ultra-high-value floatig tuable CMOS resistors. Electroics Letters, 8, vol. 44, o. 5, [7] MAUNDY, B., GIFT, S., ARONHIME P. Practical voltage/curret-cotrolled grouded resistor with dyamic rage extesio. IET Circuits Devices Syst., 8, vol., o.,. 6. [8] LANGLOIS, P., TAYLOR, J., DEMOSTHENOUS, A. Realizatio of a simle high-value grouded liear resistace i CMOS techology. I Proceedigs of ESSCIRC. Greoble (Frace, 5, [9] KUSHIMA, M., INABA, M., TANNO, K., ISHIZUKA, O. Desig of a floatig ode voltage-cotrolled liear variable resistor circuit. I The 47th IEEE Iteratioal Midwest Symosium o Circuits ad Systems. 4,. 5. [] GUPTA, M., PANDEY, R. FGMOS based voltage-cotrolled grouded resistor. Radioegieerig,, vol. 9, o. 3,. 455 to 459. [] MAHMOUD, S. A. A low voltage CMOS floatig resistor. I ICEEC 4, Iteratioal Coferece o Electrical, Electroic ad Comuter Egieerig, 4, [] GUPTA, M., PANDEY, R. FGMOS based voltage-cotrolled resistor ad its alicatios. Microelectroics Joural,, vol. 4, o. 6, [3] ZOUAOUI-ABOUDA, H., FABRE, A. New high-value floatig cotrolled resistor i CMOS techology. IEEE Trasactios o Istrumetatio ad Measuremet, 6, vol. 55, o. 3,. 7 to. [4] RIEWRUJA, V., PETCHMANEELUMKA, W. Floatig curret cotrolled resistace coverters usig OTAs. Iteratioal Joural of Electroics ad Commuicatios, 8, vol. 6, [5] SAKURAI, S., ISMAIL, M. A CMOS square-law rogrammable floatig resistor ideedet o the threshold voltage. IEEE Trasact. o Circuits ad Systems II, 99, vol. 39,. 565 to 574. [6] ELWAN, H. O., MAHMOUD, S. A., SOLIMAN, A. M. CMOS voltage cotrolled floatig resistor. Iteratioal Joural of Electroics, 996, vol. 8, o. 5, [7] WANG, S., CHAWLA, V., HA, D. S., KIM, B. Low-voltage lowower.6 GHz quadrature sigal geeratio through stackig a trasformer-based VCO ad a divide-by-two. IEEE Trasactios o Circuits ad Systems I: Regular Paers,, vol. 59, o., [8] VALERO BERNAL, M. R., CELMA, S., MEDRANO, N., CALVO, B. A ultralow-ower low-voltage class-ab fully

6 RADIOENGINEERING, VOL., NO., JUNE differetial oam for log-life autoomous ortable equimet. IEEE Trasactios o Circuits ad Systems II: Exress Briefs,, vol. 59, o., [9] PAPANANOS, Y. E. Radio-Frequecy Microelectroic Circuits for Telecommuicatio Alicatios. Lodo, (UK: Kluwer Academic Publishers, 999. [] LAHIRI, A. New CMOS-based resistorless curret-mode firstorder all-ass filter usig oly te trasistors ad oe exteral caacitor. Radioegieerig,, vol., o. 3, [] MINAEI, S., YÜCE, E., ÇIÇEKOĞLU, O. ICCII based voltagemode filter with sigle iut ad six oututs emloyig grouded caacitors. Circuits Systems ad Sigal Processig, 6, vol. 5, o. 4, [] MAHMOUD, S. A., SOLIMAN, A. M. CMOS balaced outut trascoductor ad alicatios for aalog VLSI. Microelectroics Joural, 999, vol. 3, o., About Authors... Sezai Aler TEKIN was bor i Kayseri, Turkey. He received the B. Egieerig degree from Erciyes Uiversity, Kayseri, Turkey, i, his M.S. degree from Niğde Uiversity, Niğde, Turkey, i 5, ad his Ph.D. i Electrical ad Electroics Egieerig at Erciyes Uiversity, Kayseri, Turkey i. Sice 6, he has bee a member of academic staff with Erciyes Uiversity, Egieerig Faculty, Electrical ad Electroics Det., Kayseri, Turkey. His curret research iterests iclude free sace otics, curret mode circuits, curret coveyors, electroic circuit desig ad solar cells. Hamdi ERCAN received the B. Egieerig ad M.S. degrees from Erciyes Uiversity, Kayseri, Turkey, i 4 ad 7, resectively, all i Electroic Egieerig. He received the Ph.D. i Electrical ad Electroics Egieerig at Erciyes Uiversity, Kayseri, Turkey i. Sice 5, he has bee a member of academic staff with Erciyes Uiversity, Civil Aviatio School, Avioics Det., Kayseri, Turkey. His curret research iterests iclude curret mode circuits, curret coveyors ad electroic circuit desig. Mustafa ALCI was bor i Kayseri, Turkey, i 957. He graduated at the Electroic Det. of the Techology Faculty, Gazi Uiversity, Akara, i 979. The he received the B. Sc. degree from Erciyes Uiversity, Kayseri, i 983, M. Sc. degree from the Middle East Techical Uiversity, Akara, i 986 ad Ph.D. degree from Erciyes Uiversity, Kayseri, i 989, resectively, all i Electrical & Electroics Egieerig. Sice 979, he is a member of academic staff with Erciyes Uiversity Egieerig Faculty, Electroic Egieerig Det., Kayseri, Turkey. His curret research iterests iclude image rocessig, oise ad codig artifacts suressio, fuzzy systems, medical electroics, chaotic systems ad circuit desig.