Third Op.amp. Abstract. 1. Introduction. Treatment. electronically. respect to the. aharashtra, India. responses, gains, tion. A S A 0.

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1 Circuits and Systems, 1, 1, 65-7 doi:1.46/cs Published Online October 1 ( Third Orderr Current Mode Universal Filter Usin Only Op.amp and OTAs G. N. Shinde 1, D. D. Mulajkar 1 Indira Gandhi (SR) Collee, Nanded, M Dnyanasadhana Collee, Thane, Ma shinden@yahoo.co.in Received Auust 5, 1; revised September 8, 1 Abstract Maharashtra, India aharashtra, India ; accepted September 15, 1 1. Introduction In recent years, current mode analoue sinal processin circuit techniques have received wide attention due to the hih accuracy, the wide sinal bandwidth and the sim- plicity of implementin sinal operations [1]. The desin of current mode circuits employin active devices such as OAs, OTAs, and current conveyors (CCs) have been reported in the literature [-6]. An OTA provides p a hih linear electronic tunability and wide tunable rane of its transconductance ain.ota based circuits requires no resistors; hence they are suitable for monolithic intera- tion. Recently, the multiple current output OTAs O have been used for realizin current mode filters [ 7-1]. In 1996, Tsukutani et al. proposed ood versatilee current mode biquad filter usin multiple current outputt OTAs and two rounded capacitors. This paper focuses on realization of the current-mode third order active-only filter. The proposed circuit is con- structed with OAs and dual current output OTAs. It is shown that the circuit can realize the biquadratic transfer function, and that the circuit characteristics can be elec- tronically tuned by the transconductance ains of OTAs. The proposed circuit enjoys the features of: A novel current mode active-only universal filter usin four dual current output Operational Transconduc- low tance Amplifiers (OTAs) and three Operational Amplifiers (OAs) is presented. The circuit can realize pass and hih pass filter characteristics by choosin the suitable current output branches. The filter perform are mance factors natural frequency (ω ), bandwidth ( ), quality factor and transconductance ain electronically tunable. The proposed circuit has very low sensitivities with respect to circuit active elements. From sensitivity analysis, it has been clearly shown that the proposed circuit has very low sensitivities with respect to the circuit active elements. The ain roll-off of hih pass and low pass confiuration is 18 db/octave. The proposed circuit facilitates interability, prorammability and easee of implementation. Keywords: Current Mode Filter, OTA, Bandwidth, Center Frequency, Circuit Merit Factor savin in components, realization of various filterin responses, devoid of resistors and capacitors which suits IC desin techniques, hih impedancee outputs, electronic adjustment of ω and throu uh bias currents of the active elements independent electronic adjustment of passband ains, low sensitivity fiures.. Circuit Analysis and Analytical Treatment The open loop ain of an OA is represented by the well known first order pole model [1-15] A S A S where A : Open loop D.C. ain of op-amp. : Open loop db bandwidth of the op-ampp = пf A ω : β i = ain-bandwidth product of op-amp. For S >> ω Copyriht 1 SciRes.

2 66 G. N. SHINDE ET AL. A i AS (i 1,,,) S S This model of OA is valid from a few khz to few hundred khz. In this frequency rane, OTA works as an ideal device. The OTA is characterized by the port-relation I O = m (V + - V - ) where, m is transconductance of OTA. In the dual current output OTA, the plus current output has a positive polarity, and the minus current output has a neative polarity. The analysis ives the current transfer function T = [I out / I in] as follows: T(S) = S ( ) S ( ) S mb mb1 1 mb mb 1 mb mb 1 mas ( ma 11ma) S ( ma1 ma) Sma1 (1) The circuit was desined usin coefficient matchin technique. i.e., by comparin these transfer functions with eneral third order transfer functions is iven by, S S 1S T(S) = () 1 1 S (1 ) S (1 ) S Comparin Equations (1) with () we et, ma1 1 ma 11 ma (1 ) () ma ma 1 mb1 mb (1 ) ma mb mb And ma ma It is found from above equations that circuit parameters ω, ; α can independently set and electronically tuned adjustin the transconductance ains of the OTAs. If ma, 1, and are iven, the parameter ω can be set by ma. The parameters and α can be set by ma 1 and mb respectively. It seems that the values of and α are also limited by the dynamic ranes of the OA and OTA. From (1), it can be seen that: 1) The low pass transfer function can be realized with mb mb 11 mb and mb1 mb ) The hih pass transfer function can be realized with mb mb 11 mb and mb1 mb ) The band pass transfer function can be realized with mb mb mb 11 mb The hih pass and low pass transfer functions obtained are as follows, T T HP LP S S S S ma ( ma11 ma) ma1 ma ma1 S S S ma ( ma11 ma) ma1 ma ma1 The realization of the other transfer functions invariably requires matchin the conditions in terms of the transconductance ains of the OTAs and the ain-bandwidth products of the OAs. The transconductance ains of the OTAs to realize the desired characteristics are obtained from () as ma ma1 ma 1 ma 1 ma {1 } 1 1 ma 1 ma where ω,,,, and should be iven in advance. Methods of implementin a dual current output OTA have been discussed previously (Ramirez-Anulo et al. 199, Wu 1994).. Circuit Diaram The diaram was shown in Fiure Circuit Description The proposed circuit is built with four dual current output OTAs and three OAs is as shown in Fiure (1). The V+ terminal of first OTA and V-terminal of all other OTAs are rounded. Output terminal of first OTA carryin positive polarity current is fed to invertin terminal of first OA. Its output is fed to invertin terminal of Copyriht 1 SciRes.

3 G. N. SHINDE ET AL. 67 Fiure 1. Circuit diaram of electronically tunable third order current-mode universal filter. non-invertin of third OA output of third OA is then fed to v+ terminal fourth OTA. Output terminals of all OTAs carryin positive current are fed to invertin of first OA whereas remainin current output terminals of all OTAs adds to ive output current of the circuit. The circuit can realize various third order filter functions by suitably choosin the current output branches. 5. Result and Discussion The circuit performance is studied for Central frequencies f = 1 khz and 1 MHz with circuit merit factor = 1. The eneral operatin rane of this filter is 1 Hz to 1 MHz. The value of 1 = for LF 56 N. The proposed circuit ives response only for very hih frequencies since the values of transconductance of OTAs takes very low values at frequencies less than 1 khz. The values of ma 1, maand ma are calculated by takin ma = and ma ma 1 Response is studied for = 1 for hih pass and low pass function. Fiures and shows hih pass and low pass response of the proposed filter circuit respectively. Data obtained after analysis hih pass and low pass response is iven in Tables and. From Fiures and, it is seen that the ain roll-off is 18 db/octave for both the functions and the ain stabilizes to db at frequency Hz. There is no overshoot in the response. Observed - db frequency i.e. cutoff frequency matches with desined value f. Thus the filter circuit works ideal for hih pass as well as low pass function. The values of transconductance ains for f = 1 khz and 1 MHz obtained are iven in Tables 1(a) and (b) respectively. 6. Sensitivities The practical solution is to desin a network that has low sensitivity to element chanes [14,15]. Thus sensitivity must be less than limit i.e. unity. The lower the sensitivity of the circuit, the less will its performance deviate because of element chanes. The sensitivities S and Copyriht 1 SciRes.

4 68 G. N. SHINDE ET AL. S with respect to the circuit active elements are shown in Table 4. These values are within the rane y S 1 It is found that the proposed circuit has very low sensitivity with respective to active elements. 7. Concludin Remarks A versatile current-mode active-only filter usin OAs and OTAs has been proposed. The proposed circuit can 1 GAIN(dB) GAIN (db) F1kHz F1MHz F1kHz F1MHz -7 1k 1k 1k 1M 1M FREUENCY(Hz) Fiure. Hih pass response of proposed current-mode filter GAIN(dB) GAIN (db) F1kHz F1MKz k 1k 1k 1M 1M FREUENCY (Hz) FREUENCY(Hz) Fiure. Low pass response of proposed current-mode filter. Copyriht 1 SciRes.

5 G. N. SHINDE ET AL. 69 Table 1. The values of transconductance ains. ma Value in ms for f = 1 khz ma ma1.56 ma.67 ma.19 mb mb.19 (a) for f = 1 khz Table 4. Sensitivities S and S. [1] T. Tsutani, T. Hiashimura, Y. Sumi and Y. Fukui, Electonically Tunable Current Mode Active Only Biquadratic Filter, International Journal of Electronics, Vol. 87, No.,, pp [] C.-C. Hsu and W.-S. Fen, Dynamic Decouplin and Compensatin Methods of Multi-Ais Force Sensors, International Journal of Electronics, Vol. 88, No. 1, 1, pp [] I. A. Khan and M. H. Zaidi, Multifunction Translinear-C Current Mode Filter, International Journal of Electonics, Vol. 87, No. 9,, pp [4] M. Hiashimura, Current Mode Low Pass and Band Pass Filters Usin the Operational Amplifier Pole, International Journal of Electronics, Vol. 74, No. 6, 199, pp [5] T. M. Ishida, Y. Fukui and S. Tsuiki, Novel Electronically Tunable Current Mode Filter without Eternal Passive Elements, IEEE, Vol. 1, 1996, pp [6] G. W. Roberts and A. S. Sedra, A General Class of Current Amplifier Based Biquadratic Filter Circuits, IEEE Transactions on Circuits and Systems, Vol. 9, No. 4, 199, pp [7] J. Ramirez-Anulo, M. Robinson and E. Sanchez-Sinencio, Current Mode Continuous Time Filters Two Desin Approaches, IEEE Transactions on Circuits and Systems, Vol. 9, No. 6, 199, pp [8] N. A. Shah, M. F. Rather, M. A. Malik and S. Z. Iqbal, Cascadable Electronically Tunable Sito Current Mode Active Only Universal Filter, ETRI Journal, Vol. 6, 4, pp [9] A. K. Mitra and V. K. Aatre, Low Sensitivity Hih- Frequency Active R Filters, I.E.E.E. Transactions on Circuits and Systems, Vol., No. 11, 1976, pp [1] G. N. Shinde and P. B. Patil, Sadhana, Journal of Enineerin Science, Vol. 8, No. 6,, pp [11] T. Tsukutani, M. Hiashimura, Y. Sumi and Y. Fukui, Novel Voltae-Mode Biquad Usin Only Active Devic S S ma. 1. ma1 ma ma. mb ma Value in ms for f = MHz ma ma ma ma 1.9 mb mb 1.9 (b) for f = 1 MHz Table. Analysis of frequency response of hih pass function for = 1. f F OH f F OH db/octave Gain Roll-off in stop band Octave startin at Gain Stabilization db F S 1 M 1 M 18 5 M F OH : db Frequency F S : Frequency at which ain stabilizes Table. Analysis of frequency response of low pass function for = 1. f F OL f F OL Gain Roll-off in stopband db/octave Octave startin at Gain Stabilization db F S (Hz ) M 1M 18. M 1 F OL : db Frequency realize the biquadratic transfer function and the circuit characteristics can be electronically tuned by the transconductance ains. From sensitivity analysis, it has been clearly shown that the proposed circuit has very low sensitivities with respect to the circuit active elements. The ain roll-off of hih pass and low pass confiuration is 18dB/octave. 8. References Copyriht 1 SciRes.

6 7 G. N. SHINDE ET AL. es, International Journal of Electronics, Vol. l87, No.,, pp [1] R. Nandi Active R Realization of Bilinear RL Impedances and their Applications in a Hih- Parallel Resonator and Eternal Oscillator, Proceedin of the Institute of Electrical and Electronics Enineerin, Vol. 66, No. 1, 1978, pp [1] G. N. Shinde and D. D. Mulajkar, Electronically Tunable Current-Mode Second Order Hih Pass Filter for Different Value of, International Journal of Physical Sciences, Vol., No. 6, 8, pp [14] D. R. Bhaskar, U. R. Sharma and S. M. I. Rizvi, New Current-Mode Universal Biquadratic Filter, Microelectronic Journal, Vol. 88, No. 1, 1999, pp [15] S. Minaei and S. Turkoz, Current-Mode Electronically Tunable Universal Filter Usin Only Plus-Type Current Controlled Conveyors and Grounded Capacitors, Bandpass Hih Pass Filter, ETRL Journal, Vol. 6, No. 4, 4, pp Copyriht 1 SciRes.