; Single MO-CFTA Based Current-Mode SITO Biquad Filter with Electronic Tuning
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Single MO-CFTA Based Current-Mode SITO Biquad Filter with Electronic Tuning


  • pg 1
									                                                          (IJCSIS) International Journal of Computer Science and Information Security,
                                                          Vol. 11, No. 4, April 2013

        Single MO-CFTA Based Current-Mode SITO
            Biquad Filter with Electronic Tuning
             S. V. Singh                                          R. S. Tomar                                            D. S. Chauhan
   Department of Electronics and                        Department of Electronics                                 Department of Electrical
Communication Engineering, Jaypee                     Engineering, Anand Engineering                              Engineering, Institute of
Institute of Information Technology,                       College, Agra, India                                  Technology, Banaras Hindu
        Sec-128, Noida, India                                                                                University, Varanasi-221005 (India),

Abstract— This paper presents an electronically tunable current-              consumption and the area of chip when it builds in the form of
mode single input three output (SITO) biquad filter employing                 ICs [16]. So several current-mode SIMO filters using single
single multi-output current follower trans-conductance amplifiers             active element (minimum number of active element) have been
(MO-CFTA). The proposed filter employs single resistor and two                proposed in the literature [17-22] but most of them [17-20]
grounded capacitors. The proposed filter can simultaneously realize           contain four passive elements (two capacitors and two resistors)
low pass (LP), band pass (BP) and high pass (HP) responses in                 while remaining [21-22] consists of three passive elements (two
current-mode. It is also capable of providing band reject (BR) and            capacitors and one resistors). These circuits [17-22] claim for
all pass (AP) responses without matching of components. In                    realizing two [20] or three [17-19] or all five [21-22] filtering
addition, the circuit possesses low sensitivity performance and low           functions. However, all the reported filter circuits [17-22] based
power consumption. The validity of proposed filter is verified                on single active element provide only one [18, 21, 22] or no [17,
through PSPICE simulations.
                                                                              19, 20] filtering function in the form of explicit current output.
   Keywords-component; CFTA, Biquad, Current-mode, Filter
                                                                              Explicit current outputs are necessary for the cascading of
                                                                              current-mode filter. In addition, the circuits reported in Refs. [18,
                                                                              19, 22] do not provide orthogonal electronic tunability of pole
                        I.    INTRODUCTION                                    frequency and quality factor.
     The current-mode filters, where input-output signal is
                                                                                           In this paper, a new current-mode biquad filter
represented by the branch currents of the circuits, have received
                                                                              based on single MO-CFTA is proposed. The proposed filter
significant attention owing to their large dynamic range, larger
                                                                              employs one resistor and two grounded capacitors. The proposed
bandwidth, greater linearity, simple circuitry, low power
                                                                              filter can simultaneously realize LP, BP and HP responses in
consumption and less chip area over their voltage-mode counter
                                                                              current form in which two of the outputs (LP, BP) are explicitly
parts, where input-output signal is represented by node voltage of            available. In addition, the pole frequency and quality factor of
the circuits[1-2]. They can be classified as single-input
                                                                              the proposed current-mode filter circuit can be tuned
multiple-output (SIMO) or multiple-input single-output
                                                                              electronically and orthogonally. The circuit possesses low
(MISO). There has been a great attention on the design and
                                                                              sensitivity performance and low power consumption. The
study of current-mode SIMO filter due to simultaneous
                                                                              validity of proposed filter is verified through PSPICE, industry
realization of multi-function filtering outputs, without
                                                                              standard tool.
changing the connection of the input current signal and
without current signal matching. During the last one decade and
recent past a number of universal current-mode SIMO active                        II.    MO-CFTA AND PROPOSED CURRENT MODE FILTER
filters have been reported in the literature [3-15, 17-22], using                A MO-CFTA is a combination of current follower and multi-
different electronically tunable current-mode active elements                 output transconductance amplifier. The properties of ideal MO-
such as CCCII [3-6], OTA[7-8], CDTA[9,10,18,21], CFTA[11-                     CFTA can be characterized by the following set of equations
13], CCCCTA[14-15], CCTA[17] and VDTA[22] etc. where
CCCII, OTA, CDTA, CFTA, CCTA, CCCCTA and VDTA                                 Vf = 0 , I ± Z = ± If , I ± X = ±g m VZ                               (1)
stand for current controlled current conveyor, operational
transconductance         amplifier,       current         differencing
transconductance amplifier, current follower transconductance
amplifier, current conveyor transconductance amplifier, current
controlled current conveyor transconductance amplifier and
voltage differencing transconductance amplifier, respectively.
The current-mode filters reported in Refs.[3-15] realize multi-
filtering functions but they contain six [3], five [4 ], four [12,13],
three [5-6,10-11, 14-15], two [9] active elements which are
excessive in numbers. On the other hand, the active filter
employing low active components is more beneficial from
fabrication point of view. Moreover, it can also reduce the power                                      Fig. 1. MO-CFTA Symbol

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                                                                                                             ISSN 1947-5500
                                                            (IJCSIS) International Journal of Computer Science and Information Security,
                                                            Vol. 11, No. 4, April 2013

   where gm is trans-conductance of the CFTA. The gm                          IBP together, respectively. The pole frequency (ω0) and quality
depends upon the biasing current IS of the CFTA. The                          factor (Q) of the proposed circuit is given by
schematic symbol of CFTA is illustrated in Fig. 1. For MOS
implementation of CFTA [10], the gm can be expressed as                                                                    1

                                                                              ωO =
                                                                                                           (βn I S ) 2
gm = βnIS                                                          (2)                 RC1C2                RC1C2

   where βn is given by
                                                                                                          ( βn I S )
                  W                                                                  C2                                  2   C2
 β n = µ n C OX                                                  (3)        Q=              =                                                      (8)
                  L                                                                 Rg m C1                  R               C1
    where µn, COX are the electron mobility, gate oxide                          From (7) and (8), it can be remarked that both the ωo and Q
capacitance per unit area and W/L is the transistor aspect ratio              can be electronically tuned through biasing current IS. In
of NMOS, M19 and M20 forming a differential pair in the TA                    addition, ωo and Q are orthogonally adjustable with adjustment
stage of employed MO-CFTA as shown in Fig. 3.                                 of gm and R such that product gmR remain constant and
                                                                              quotient gm/R varies and vice versa. The active and passive
                                                                              sensitivities of the proposed circuit as shown in Fig. 2, can be
                                                                              found as

                                                                                  ω                1 ω0             1
                                                                                 SC10,C2 , R = −     , S βn , I S =                                  (9)
                                                                                                   2                4
                                                                                           1 Q              1 Q 1
                                                                                SC1 , R = − , S βn , I S = − , SC2 =
                                                                                           2                4        2
                                                                                  From the above results, it can be observed that all the
                                                                              active and passive sensitivities are low and within half in

                                                                                                   III.     SIMULATION RESULTS
                                                                                   In order to confirm the practical validity of the proposed
                                                                              filter circuit, it was simulated in PSPICE using the MOS
                                                                              implementation of MO-CFTA as shown in Fig. 3, with the
       Fig. 2. Proposed MO-CFTA based current-mode biquad filter              transistor model of 0.35µm MOSFET from TSMC whose
                                                                              model parameters are given in Table 1. DC power supplies
    The proposed current-mode biquad filter with single input                 were selected as Vdd = -Vss= 1.5V and Vbb= 0.45V. To obtain
and three outputs is shown in Fig. 2. It is based on single MO-               fo=ωo/2π=1.35MHz at Q=1, the active and passive components
CFTA, single resistor and two grounded capacitors. Routine                    were chosen as IS =50.5µA, R = 6K and C1=C2= 20pF. Aspect
analysis of the proposed circuit yields the following current                 ratio of MOS transistor is given in Table 2. Fig. 4 shows the
transfer functions.                                                           simulated current gain responses of the LP, BP and HP of the
                                                                              proposed filter. Fig. 5 shows the gain and phase responses of
I LP          gm                                                              BR and AP filtering functions. The simulation results show the
     =                                                             (4)        simulated pole frequency as 1.29 MHz that is ~4% in error
I in RC1C2 s + Rg mC1s + g m
                                                                              with the theoretical value. The power dissipation of the
                                                                              proposed circuit for the design values was found as 1.18 mW
                                                                              that is a low value. Next, the tuning aspect of pole frequency
I BP        − Rg mC1 s
     =                                                             (5)        was tested for constant Q (=1) through simulation of BP
I in RC1C2 s 2 + Rg mC1 s + g m                                               responses. The bias current IS (gm) and R were varied for three
                                                                              sets of values in such a way so that gmR remain constant and
                                                                              other parameters were chosen as C1=C2= 20pF. The pole
I HP          RC1C2 s 2                                                       frequency variation is shown in Fig. 6. The pole frequency
     =                                                             (6)
 I in RC1C2 s 2 + Rg mC1s + g m                                               was found to very as 620 KHz, 1.29 MHz and 1.96 MHz for
                                                                              three different sets of values of IS (gm) and R as mentioned in
                                                                              Fig. 6. Similarly, Fig. 7 shows the gain responses of BP
It is clear from (4) – (6) that the proposed current-mode filter              function, for different values of R and IS to indicate the tuning
can realize LP, BP and HP responses. The circuit is also                      of quality factor of the proposed filter circuit, with out
capable of realizing BR and AP by adding ILP, IHP and ILP, IHP,               affecting the pole frequency.
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                                                                                                              ISSN 1947-5500
                                                                (IJCSIS) International Journal of Computer Science and Information Security,
                                                                Vol. 11, No. 4, April 2013

                                                         Fig. 3. CMOS Implementation of MO-CFTA


Fig. 4. Gain responses of LP, BP and HP for the proposed current-mode filter

Further, simulations were carried out to verify the total
harmonic distortion (THD). The circuit was verified by
applying a sinusoidal voltage (Iin) of varying frequency and
amplitude of 20µA. The THD measured at the LP output were
found to be less than 4% while frequency was varied from 100
KHz to 500 KHz. The time domain behavior of the proposed
current-mode filter was also investigated by applying a 500
KHz sinusoidal input current signal with peak to peak
amplitude of 40µA. Fig. 8 shows the time domain sinusoidal
current input and corresponding LP output waveform for the
proposed filter.
    Further, the Monte Carlo analysis of the proposed circuit                                                                          (b)
for C1 = C2 = 20 pF was also performed taking 15% tolerances
                                                                                    Fig. 5. Gain and phase response of (a) BR and (b) AP filtering functions for
in the capacitive components. The analysis was done for six                                              the proposed current-mode filter
runs. The time domain response of current-mode LP output
(ILP) is shown in Fig. 9. It is observed that 40µA peak to peak
input current sinusoidal signal levels having frequency 500
KHz are possible without significant distortions.

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                                                                                                                  ISSN 1947-5500
                                                              (IJCSIS) International Journal of Computer Science and Information Security,
                                                              Vol. 11, No. 4, April 2013

Table 1. The SPICE model parameters of MOSFET for level 3, 0.35 µm
                    CMOS process from TSMC

     NMOS         LEVEL=3     TOX=7.9E-9    NSUB=1E17
               GAMMA=0.5827871 PHI=0.7 VTO=0.5445549
               DELTA=0         UO=436.256147     ETA=0
               THETA=0.1749684           KP=2.055786E-4
               VMAX=8.309444E4         KAPPA=0.2574081
               RSH=0.0559398 NFS=1E12 TPG=1 XJ=3E-7
               LD=3.162278E-11          WD=7.046724E-8
               CGDO=2.82E-10 CGSO=2.82E-10 CGBO=1E-
               10 CJ=1E-3    PB=0.9758533 MJ=0.3448504
               CJSW=3.777852E-10 MJSW=0.3508721

     PMOS          LEVEL=3    TOX=7.9E-9    NSUB=1E17
               GAMMA=0.4083894       PHI=0.7    VTO=-
               0.7140674    DELTA=0     UO=212.2319801
               ETA=9.999762E-4        THETA=0.2020774
               KP=6.733755E-5        VMAX=1.181551E5
               KAPPA=1.5 RSH=30.0712458 NFS=1E12
               TPG=-1      XJ=2E-7     LD=5.000001E-13
               WD=1.249872E-7           CGDO=3.09E-10
               CGSO=3.09E-10 CGBO=1E-10 CJ=1.419508E-
               3 PB=0.8152753 MJ=0.5 CJSW=4.813504E-10

              Table 2. Dimensions of MOS Transistors
   NMOS Transistors                     W (um) / L (um)
   M8-M12 & M16-M18                     0.7 / 0.35
   M19, M20                             4.0 / 1.0
   M28-M32                              4.0 / 1.0
   PMOS Transistors                     W (um) / L (um)
   M1,M5,M6                             1.4 / 0.35
   M7                                   5.6 / 0.35
   M2-M4 & M13-M15                      2.8 / 0.35                                         Fig.7. BP responses showing quality factor tuning
   M21-M27                              4.0 / 1.0

                                                                              Fig. 8. The time domain sinusoidal current input and corresponding current-
                                                                                                           mode LP output

                                                                                                        IV.    CONCLUSION
                                                                              In this paper, an electronic tunable current-mode biquad filter
                                                                              with single input and three outputs using only single MO-CFTA,
                                                                              one resistor and two grounded capacitors has been presented.
                                                                              The proposed current-mode filter can simultaneously realize LP,
         Fig. 6. BP responses showing pole frequency tuning                   BP and HP responses. it is also capable of realizing BR and AP

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                                                                                                            ISSN 1947-5500
                                                                    (IJCSIS) International Journal of Computer Science and Information Security,
                                                                    Vol. 11, No. 4, April 2013

filtering functions. In additions, it also offers several advantages,                    [12] J. Satansup and W. Tangsrirat, “Single input five output electronically
                                                                                              tunable current-mode biquad consisting of only ZC-CFTAs and
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                                                                                         [18] D. Prasad, D. R. Bhaskar and A. K. Singh, “Universal current-mode
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[1]  B. Wilson, “Recent developments in current mode circuits,” Proc. IEE.,              [22] D. Prasad, D. R. Bhaskar and M. Srivastava, “Universal current-mode
     Pt. G, vol. 137, pp. 63-77, 1990.                                                        biquad filter using a VDTA,” J. Circuits and Systems, vol. 4, pp. 32-36,
[2] G. W. Roberts and A. S. Sedra, “All current-mode frequency selective                      2013.
     circuits,” Electronics Lett., vol. 25, pp. 759-761, 1989.
[3] M. T. Abuelma'atti and N. A. Tassaduq, “A novel single-input multiple-                                            AUTHORS PROFILE
     output current-controlled universal filter,” Microelectronics J., vol. 29,          S. V. Singh was born in Agra, India. He received his B.E. degree (1998) in
     pp. 901-905, 1998.                                                                  Electronics and Telecommunication from NIT Silchar, Assam (India), M.E.
[4] S. Minaei and S. Türköz, “New current-mode current-controlled                        degree (2002) from MNIT Jaipur, Rajasthan (India) and Ph.D. degree (2011)
     universal filter with single input and three outputs,” Int’l J. Electronics,        from Uttarakhand Technical University. He is currently working as Assistant
     vol. 88, pp. 333-337, 2001.                                                         Professor in the Department of Electronics and Communication Engineering
[5] S. Maheshwari and I. A. Khan, “Novel cascadable current-mode                         of Jaypee Institute of Information Technology, Noida (India) and has been
     translinear-C universal filter,” Active Passive Electronic component, vol.          engaged in teaching and design of courses related to the design and synthesis
     27, pp. 215-218, 2004.                                                              of Analog and Digital Electronic Circuits. His research areas include Analog
                                                                                         IC Circuits and Filter design. He has published more than 20 research papers
[6] R. Senani, V. K. Singh, A. K. Singh, and D. R. Bhaskar, “Novel
                                                                                         in various International Journal/Conferences.
     electronically controllable current mode universal biquad filter,” IEICE
     Electronics Express, vol. 1, pp. 410-415, 2004.                                     R. S. Tomar was born in Aligarh, India. He obtained his B. E (1995) from
                                                                                         Bombay University, M. E. (2004) from Agra. He is currently associated with
[7] T. Tsukutani, M. Ishida, S. Tsuiki and Y. Fukui, “Versatile current-mode
                                                                                         Anand Engineering College, Agra. His research areas include designing of
     biquad filter using multiple current output OTAs,” Int’l J. Electronics,
     vol. 80, no. 4, pp. 533-541, 1996.                                                  microwave and analog circuits. He has published no. of papers in National and
                                                                                         International Conferences.
[8] D. R. Bhaskar, A. K. Singh, R. K. Sharma and R. Senani, “New OTA-C
                                                                                         D. S. Chauhan was born in Dholpur, India. He obtained his B.Sc Engg.(1972)
     universal current-mode/trans-admittance biquads,” IEICE Electronic
                                                                                         in Electrical Engineering at I.T. B.H.U., M.E. (1978) at R.E.C. Tiruchirapalli (
     Express, vol. 2, no. 1, pp. 8-13, 2005.
                                                                                         Madras University ) and PH.D. (1986) at IIT/Delhi. His brilliant career
[9] A. U. Keskin, D. Biolek, E. Hancioglu and V. Biolkova, Current-mode                  brought him to teaching profession at Banaras Hindu University where he was
     KHN filter employing current differencing transconductance amplifiers,              Lecturer, Reader and then has been Professor till today. He has been director
     Int’l J. Electronics and Communications (AEÜ), vol. 60, pp. 443-446,                KNIT Sultanpur in 1999-2000 and founder vice Chancellor of U.P.Tech.
     2006.                                                                               University (2000-2003-2006). Later on, he has served as Vice-Chancellor of
[10] D. Biolek and V. Biolkova, “CDTA-C current-mode universal 2nd order                 Lovely Professional University (2006-07) and Jaypee University of
     filter,” Proceeding of the 5th Int. Conf. on Applied Informatics and                Information Technology (2007-2009). Currently he has been serving as Vice-
     Communications, pp. 411-414, 2003.                                                  Chancellor of Uttarakhand Technical University. He has supervised 24 Ph.D.,
[11] N.Herencsar, J. Koton, K.Vrva and A. Lahiri, “Novel mixed-mode KHN                  one D.Sc. He has authored two books and published and presented 170
     equivalent filter using Z-copy CFTAs and Grounded Capacitors, “Latest               research papers in international journals and international conferences. His
     Trenda On Circuits, Systems and Signals, pp. 87-90, 2010.                           research areas include Analog IC Circuits and Control Systems design.

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