FIRST ORDER TRANSFER SECTIONS WITH RECONNECTION LESS ELECTRONICALLY RECONFIGURABLE HIGH PASS, ALL PASS AND DIRECT TRANSFER CHARACTER

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1 Journal o ELECTRICAL ENGINEERING, VOL 67 (26), NO, 2 2 FIRST ORDER TRANSFER SECTIONS WITH RECONNECTION LESS ELECTRONICALLY RECONFIGURABLE HIGH PASS, ALL PASS AND DIRECT TRANSFER CHARACTER Roman Sotner Jan Jerabek Norbert Herencsar Roman Prokop Abhirup Lahiri Tomas Dostal Kamil Vrba Presented research introduces active iltering circuits which allow change o the transer type without necessity o reconnection o the input or output terminal that can be very useul or on-chip applications. Our attention is ocused on simple irst-order ilters that allow high-pass response (HP), all-pass response (AP) and also direct transer (DT) with constant magnitude and phase characteristics between two terminals (input and output) by adjusting o one controllable parameter (current gain B in our case). Useul modiication o the well-known current ollower transconductance ampliier (CFTA), the so-called Z-copy current-controlled current ollower dierential input transconductance ampliier () and adjustable current ampliier were utilized in these circuits. Interesting possibilities (crossing between several transer unctions) o presented circuits require dierent values o B to obtain desired transer unction that is very important or practice and selection o speciic way o control. Requirements on value o this continuously controllable gain B dier among presented structures. Theory is supported by simulation and measurement results with behavioral models utilizing commercially available active elements and simulation results with active elements based on CMOS models. K e y w o r d s: active ilters, electronic control, reconiguration, reconnection-less multiunction, Z-copy current-controlled current ollower dierential input transconductance ampliier, INTRODUCTION Many suitable active elements or circuit synthesis o various applications have been presented in literature []. Some o them allow interesting eatures and give useul possibilities o electronic control in applications. However, their urther modiications bring some additional advantages that are not available in their basic orms and deinitions. These improvements mean additional implementation o controllable parameters in the active element in the most cases. We know our types o electronic control in rame o the active element. The irst group utilizes controllable transconductance (g m ) [, 2]. The second group deals with controllable intrinsic resistance (R x ) o the current input terminal (mainly in current-mode active elements) [3]. Control o current gain (B ) [4] becomes very popular in recent years mainly [5 ]. Utilization o the adjustable voltage gain (A) is also very useul in many cases, but complexity o active elements is worse [2] than basic structures utilizing g m or R x control [2, 3]. Design o active elements in combination o several (at least two) types o control in rame o one active element is one o today s trends [3 9]. We prepared overview o combined active elements employing current ollower/inverter and transconductance subparts. Active elements combining current inverter and transconductance ampliier have been already investigated precisely. For example current inverter transconductance ampliier (CITA) and its modiications (using so-called Z-copy technique [2]) were reported in recent literature [2]. Active elements presented in previously discussed work have only one possibility o control by electronically adjustable transconductance. We provided detailed comparison o the CFTA/CITAbased circuit structures (or their modiications) that provide irst- and/or second- order transer unctions, to see recent progress in the ield o CFTA/CITA-based irstorder ilters. Solutions discussed in [2 25] are simple irst-order circuits. Some o them provide also universal [23] or multiunctional iltering characteristics [24]. Typical distinctiveness o the multiunctional/universal ilters is the necessity o physical reconnection o the input or output terminal or change o the transer type. Change o the transer unction o the ilter is quite important eature o applications on the chip. This eature is required i direct connection between two nodes Department o Radio Electronics, Department o Telecommunications, Faculty o Electrical Engineering and Communication, Brno University o Technology, Technicka 382/2, 66 Brno, Czech Republic, sotner@eec.vutbr.cz; Department o Microelectronics, Faculty o Electrical Engineering and Communication, Brno University o Technology, Technicka 358/, 66 Brno, Czech Republic; D3-Friends Apartments, IP Extension, Delhi, India Department o Technical Studies, College o Polytechnics, Jihlava, Tolsteho, 6, 586, Jihlava, Czech republic DOI:.55/jee-26-2, Print (till 25) ISSN , On-line ISSN X c 26 FEI STU

2 Journal o ELECTRICAL ENGINEERING 67, NO, 26 3 Table. Comparison o the parameters o presented solutions to recently reported reconnection-less voltage-mode iltering structures based on other active elements Active elements (number) [26] ECCII- (), VB () [27] Type o unctions biquadratic (2 nd order) ECCII- (4), MO-CF/I (2), VB biquadratic () or OTA (5), VB () (2 nd order) Available transer unctions AP, BR AP, BR [28] OTA (2), ECCII-() st order AP, LP, idt [29] ZC-CG-VDCC () st order AP, LP, idt, DT Fig. 3a (), CA () st order ihp, AP, idt Fig. 3b (), CA () st order HP, iap, DT Abbreviations: ECCII- Current Conveyor o Second Generation (negative) with possibility o gain adjusting between X and Z terminal OTA Operational Transconductance Ampliier VB Voltage Buer CA Current Ampliier (adjustable gain B) MO-CF/I Multiple-output Current Follower/Inverter ZC-CG-VDCC Z-copy Controlled-Gain Voltage Dierencing Current Conveyor DT direct transer idt inverted direct transer BR band reject transer unction AP all-pass transer unction iap inverting all-pass transer unction LP low-pass transer unction HP high-pass transer unction ihp inverting high-pass transer unction (in rame o the complex communication system subblocks) have to be replaced by HP or other ilter response in order to reject some type o wide-band or selective noise or distortion. It is necessary to provide reconnection o the output by switches, it practice. However, some types o the ilter with speciic eatures (reconnection-less reconigurable) allow change o the transer unction by simple tuning o externally adjustable parameter [26] no physical/electrical reconnection is necessary. Recently reported reconnection-less iltering circuits were summarized in Tab. or easy comparison. Solution discussed in [26] allows change o the 2nd-order transer unction between AP and BR by adjustable current gain. Solution o some drawbacks o [26] was discussed in ull state variable ollow the leader structure presented in [27]. However, circuit is quite complicated. The irst order reconnection less ilters were presented also in [28, 29]. Both realizations, are ocused on reconiguration between AP, LP and direct transer (DT). Unortunately, no realization reported in the past (Tab. ) was ocused on AP, HP and DT transer unctions that can be changed electronically. For more details see Tab.. This paper is ocused on simple st -order circuits where additional adjustable current ampliier was en- I SET_R (a) I SET_R I V V I I V x ZC Z v I ZC I Z V I R I ZC = I I Z = I OTA (b) I = g m (V Z V V ) x x I = g m (V Z V V ) V ZC V Z V v ZC Z v Fig.. Principle o the : (a) symbol, (b) behavioral model

3 4 R. Sotner et al: FIRST-ORDER TRANSFER SECTIONS WITH RECONNECTION-LESS ELECTRONICALLY... V DD = +V M 2 M 2 M9 M 22 M 23 M 24 M 25 M 26 M 27 M 28 M 29 M 3 M 3 I SET_R M M 2 M 3 M 4 zc z M 7 M 8 v M 5 M 6 M 7 M 8 M 9 M M M 2 V SS = -V M 4 M 3 I SET_gm M 5 M 6 Fig. 2. Possible internal CMOS topology o proposed active element I SET_R I SET_R Z ZC I SET_ B Z ZC I SET_ B V inp CA V out V inp CA V out C B R L C B R L (a) (b) Fig. 3. HP/AP structures utilizing single ZC-CCCFDTA and adjustable current ampliier: (a) using non-inverting controllable current ampliier, (b) using inverting current ampliier gaged to obtain several types o transer characteristics including direct connection (non-inverting or inverting) between input and output terminal (the same orm o the numerator and denominator o the transer unction transer with constant magnitude and phase characteristic) in several very simple circuits. The paper is organized as ollows: Section 2 shows deinition o presented modiication o active element (socalled Z-copy current-controlled current ollower dierential input transconductance ampliier ) and possible way o its CMOS implementation. Chapter 3 deals with st-order electronically reconigurable transers (HP, AP, DT) in simple circuits based on ZC- CCCFDITA and adjustable current ampliier with minimal number o passive elements and their theoretical analysis. Section 4 introduces method o implementation o the by commercially available active elements (behavioral model) and its application in selected type o the reconigurable iltering solution together with CMOS implementation. Comparison o ideal and simulated results with CMOS and behavioral model is also presented. Exemplary experimental results are given in Section 5. Summarization o achieved eatures, requirements and results is provided in conclusion. 2 Z COPY CURRENT CONTROLLED CURRENT FOLLOWER DIFFERENTIAL INPUT TRANSCONDUCTNACE AMPLIFIER The Z-copy current-controlled current ollower dierential input transconductance ampliier () belongs to amily o modern active elements [] deeply investigated by Herencsaret al, [3]. Principle o this useul modiication o basic CFTA is in controllable input intrinsic resistance R, transconductance (g m ) o the output section and additional dierential voltage input [25] o the output (transconductance section OTA). Basic CFTA does not use ully-dierential input o the OTA

4 Journal o ELECTRICAL ENGINEERING 67, NO, xOPA66/86 + DVB DT R B C 5 E R 2 AD83 5 /g m + VCA6/8 A CF/I VCA EL483 E B C V SET_R ZC Z DT 2 Fig. 4. Behavioral model o the employing commercially available active devices section (one input terminal is grounded) [], however, it seems to be advantageous. Principal conception o the is shown in Fig.. Input current I is mirrored to two output terminals o the irst section (current ollower). One current output is connected directly to the second (output) section based on operational transconductance ampliier (OTA) and called z. The second auxiliary current output o the irst section is identical copy o the input current I, this output is called zc. Negative input o the OTA section is lead out o the device and noted as v. Two current outputs o the OTA section have both polarities or we can use multiple-output OTA section. Principle is clear rom Fig. b. The CMOS structure utilizing current controlled current conveyor o second generation [3] connected as multiple-output current ollower and dual-output OTA section [2, 22] is shown in Fig. 2. Controllable intrinsic resistance is given by [3, 32] R =, () W I SET R K M,2 W Pn L M,2 + I SET R K M3,4 Pp L M3,4 and transconductance o the output OTA section has known expression [3] g m = 2 V I SET gm K Pn W M7,8 L M7,8 (2) where constant 2 is given by gain o current mirrors (P-MOS: M 28 M 27 and M 29 M 3 ) and K P n,p are technological constants (µ C ox ) o used abrication technology [33] (TSMC.8 µm). 3 FIRST ORDER FILTERS WITH ELECTRONICALLY RECONFIGURABLE TYPE OF THE TRANSFER FUNCTION Almost all active electronic systems are integrated on chip today. Electronic adjustability o the systems is important or control o bandwidth, pole requency, oscillation requency, quality actor, etc. However, extensive reconiguration like change o the transer unction o the requency ilter is not possible because it requires change o topology, reconnection o input/output nodes (SIMO, MISO types) very oten. Unortunately, ater abrication no change o the internal structures is possible. We present simple st-order transer unctions that are available in advanced circuitry as HP or AP response without necessity o changing the topology or reconnection o nodes (SISO single input and single output type). Only electronically adjustable parameter is used or change type o the transer unction. Thereore this way can be very useul or on-chip subsystems. We will demonstrate principle on two solutions both are practically the same but dierent conigurations o polarities o the outputs o active elements give us signiicantly dierent possibilities. Circuit in Fig. 3a is HP/AP ilter and DT based on and Adjustable Current Ampliier. It has both o the z and zc terminals with positive polarity. Transer unction has orm K (s) = g mr L R B scr g m + sc. (3) The circuit structure behaves as inverting HP (ihp) section or B =. AP section is available or B = or a condition g m = /R. Inverting direct transer (idt) is set by B =. Zero and pole requencies are given by ω z = B/R C and ω p = g m /C. Independent control o the zero and pole location (outside pure AP behavior) is possible also by R and g m (bilinear ilter). However, both parameters inluence passband gain. The second solution o the ilter has the same circuit solution but direction (polarity) o output currents rom outputs and auxiliary terminal z are opposite, see Fig. 3b. This dierence is important or type (polarity) and value o controllable current gain B. Despite the act that both circuits have the same structure, transer unction o the solution in Fig. 3b is slightly dierent K 2 (s) = g mr L R 2 B + scr g m + sc, (4) where B = gives DT response (constant unity magnitude and phase equal to degrees) i g m = /R. The transer unction o HP response is obtained in case o B = 2 and the inverting AP (iap) response is available or B = 3 (g m = /R ). Zero requency is given by ω z = (2 B)/R C and pole requency is the same as in the previous case (ω p = g m /C). The irst case (Fig. 3a) requires controllable parameter B or change o the transer type rom HP to AP response, the second case (Fig. 3b) allows change also rom HP to AP, but or B 2. Migration o zero rom let to the right side o the complex space is conditioned by both polarities o B (B = ±) in the irst case in Fig. 3a, which is sophisticated task or current ampliier. Fortunately, solution in Fig. 3b allows migration o zero just

5 6 R. Sotner et al: FIRST-ORDER TRANSFER SECTIONS WITH RECONNECTION-LESS ELECTRONICALLY... K(dB) ideal (deg) 6 B = 3 (AP) - -2 behavioural model 2 8 B = 2 (HP) -3-4 CMOS model (Hz) 7 8 Fig. 5. HP magnitude response obtained rom structure utilizing behavioral or CMOS model o and adjustable current ampliier 2 - K(dB) B = (direct transer) -2 B = 3 (AP) (Hz) 7 8 Fig. 7. All phase responses obtained rom structure utilizing behavioral and CMOS models o and adjustable current ampliier (three discrete current gains) 4 B = (direct transer) (Hz) Fig. 6. AP and DT magnitude responses obtained rom structure utilizing behavioral and CMOS models o and adjustable current ampliier EL282 [35] and diamond transistor OPA86 [39, 4]). Supply voltage o the behavioral model was ±5 V. Discussed model employs controllable current ampliier/ ollower part that allows voltage control o the R based on voltage controllable ampliier (VCA) (method irstly proposed in [4]). The resistance R is given by [4] as R = R ( + 2(V SET R +) ). (5) Dierential voltage ampliier (DVB) can be easily replaced by the second VCA to control also the current gain [4]. Resistor R 2 serves as voltage/current converter. Transconductance section is utilized by two diamond transistors (DTs). I SET_R in one polarity o the B. Necessity o higher gain B = 3 (or AP response) is small disadvantage o this solution (higher gain = higher power consumption in many cases). Both circuits are suitable or cascading (high-impedance input terminal). This solution will be analyzed in more details in Chapter 4. C p R p C x Z ZC v V inp I SET_ B CA C p2 V out 4 SIMULATION RESULTS B R L 4. Simulation o the selected iltering solution C Circuit in Fig. 3b was chosen or detailed study. Its eatures are interesting or investigation because it allows HP, AP and DT unctions simultaneously in one circuit structure (without reconnection) only by change o parameter B (in one polarity). The rest o parameters was selected as: R = R L = kω, C = 47 pf, g m = ms. Current ampliier constructed rom EL282 [35] was used or control o loop-gain and type o the transer (commercially available devices-based behavioral model). We prepared the ollowing behavioral model (Fig. 4) o the based on commercially available devices (VCA6/8 [36], AD83 [37], EL483 [38], Fig. 8. Model representing the most important parasitic inluences in circuit rom Fig. 3b CMOS structure rom Fig. 2 was also used (ater appropriate changes o polarities o the outputs and auxiliary terminals in accordance to Fig. 3b) or simulation together with CMOS current ampliier based on section used also in [, 2] and [29] especially or example. Its current gain [34] is given by B = NI b2 I b2 =. (6) 2I set B I set B

6 Journal o ELECTRICAL ENGINEERING 67, NO, K (db) R p = k R p =25 k R p = k R p = M B = (Hz) 8 (a) K (db) B = 2 B = 2.4 B = 2.4 R p = 25 k (Hz) (b) Fig. 9. HP response behavior under conditions o parasitic elements: (a) stepping o R p while B is constant, (b) stepping o B while R p is constant Figure 5 shows magnitude HP response or three traces: ideal ( p = 339 khz or B = 2, g m = ms, R = kω), simulation with behavioural model ( p = 296 khz or V SET B = 2.46 V, g m = ms, V SET R = V) and simulation with CMOS model ( p = 378 khz or I SET B = 56.5 µa, I SET gm = 54 µa I SET R = 34 µa) using the device. Figure 6 indicates reconigurability between AP, HP and direct transer in phase response. There ideal traces, simulation results with behavioural model and simulation results with CMOS model o the are compared. The ideal trace, behavioural model and CMOS model responses are distinguished by style o the line (ideal trace - thin solid line, behavioural model thick line, CMOS model thick dashed line). Sets o parameters (in order to obtain AP or ideal B = 3, HP or ideal B = 2 and direct transer or ideal B = ) are ollowing: AP (behavioural model - p = 292 khz, V SET B = 4 V, g m = ms, V SET R = V; CMOS model - p = 373 khz, I SET B = 35 µas, I SET gm = 54 µa, I SET R = 34 µa), HP (behavioural model - 3dB = 296 khz, V SET B = 2.46 V, g m = ms, V SET R = V; CMOS model - 3dB = 378 khz, I SET B = 56.5 µa, I SET gm = 54 µa, I SET R = 34 µa), direct transer (behavioural model - V SET B =.5 V, g m = ms, V SET R = V; CMOS model - I SET B = 8 µa; I SET gm = 54 µa; I SET R = 34 µ A). Magnitude responses or DT and HP coniguration are given in Fig. 7. Sets o parameters is the same as note above (or AP and DT). Supply voltage was always ±5 V or behavioural model and ± V or CMOS model. 4.2 Parasitic analysis o selected iltering solution We provided detailed analysis o important parasitic inluences in the selected structure (Fig. 3b). Main problems create additional impedance in high-impedance node o working capacitor and parasitic capacitance in node o working resistor R L (in parallel). Model representing these problems is depicted in Fig. 8. We suppose ollowing simpliications, because they are nearly always ulilled: R ZC R inpca, R x R L thereore, we can suppose R L in node operating as only dominant resistance. Parasitic elements are estimated (determined rom behavioral model in Fig. 4 or example) as ollows: R p R R z R x + R 25 kω, C p C + C z + C x + pf, C p2 C out CA + C x pf. We used also simpliication C = C + C p. The rest o parameters was used as in case o Section 4.. Low value o R x± (25 kω [39, 4]) seems to be the most important problem or us. Approximate equation or overall transer unction o the ilter has orm in this case K 2 (s) = g mr L ( Rp (2 B) + R + sc R R p )/( gm R R p + R + s [R R p C + R L C p2 (g m R R p + 2R p + R )] + s 2 C C p2 R R p R L ). (7) Simulation results o the HP response (that is the most inluenced by parasitic behavior) we have shown in Fig. 9. O course R p has direct impact on zero location and value o inite attenuation in the stop band, see Fig. 9a. Ideal value B = 2 is expected or pure HP response without zero. Existence o real R p causes unintentional creation o zero also or B = 2. However, problem o low R x± (the most important contributor o R p ) can be still easily solved by B control (as we suppose to utilize or reconiguration) to compensate impact o R p and to obtain pure HP again (or B = 2.4), see Fig. 9b. Second order denominator o inluenced transer unction has also impact on pass-band transer drop at higher requencies (but maybe lower than available bandwidth o active elements in some cases) that is visible in all transer responses (HP, iap, DT). Estimation o this pole requency can be provided rom: ω p2 = /RL C p2 = 6 MHz. 5 EXPERIMENTAL RESULTS We measured discussed type o the ilter (Fig. 3b) based on behavioral model rom Fig. 4 and additional current ampliier (EL282) under the same conditions as described in Section 4. Measurements were provided by network vector analyzer ENA E57C. Brie exemplary results o the ilter conigurations, particularly HP, iap

7 8 R. Sotner et al: FIRST-ORDER TRANSFER SECTIONS WITH RECONNECTION-LESS ELECTRONICALLY... Fig.. Measured magnitude and phase response o HP coniguration, V set B = 2.6 V Fig.. Measured magnitude and phase response o iap coniguration, V set B = 4.3 V Fig. 2. Measured magnitude and phase response o DT coniguration, V set B = V and DT transers, are shown in Figs. 2. Experimental results are close to expectations and behavior o simulated case. Acknowledgement Research described in this paper was inanced by Czech Ministry o Education in rame o National Sustainability Program under grant LO4. For research, inrastructure o the SIX Center was used. Research described in the paper was supported by Czech Science Foundation project under No P. Reerences [] BIOLEK, D. SENANI, R. BIOLKOVA, V. KOLKA, Z. : Active Elements or Analog Signal Processing: Classiication, Review and New Proposals, Radioengineering 7 No. 4 (28), [2] GEIGER, R. L. SÁNCHEZ-SINENCIO, E. : Active Filter Design using Operational Transconductance Ampliiers: a Tutorial, IEEE Circ. and Devices Magazine (985), [3] FABRE, A. SAAID, O. WIEST, F. BOUCHERON, C. : High Frequency Applications based on a New Current Controlled Conveyor, IEEE Trans. on Circuits and Systems - I 43 No. 2 (996), [4] SURAKAMPONTORN, W. THITIMAJSHIMA, W. : Integrable Electronically Tunable Current Conveyors, IEE Proceedings-G 35 No. 2 (988), [5] H. ALZAHER : CMOS Digitally Programmable Quadrature Oscillators, International Journal o Circuit Theory and Applications 36 No. 8 (28), , DOI:.2/cta.479. [6] ALZAHER, H. TASADDUQ, N. AL-EES, O. Al-AMMA- RI, F. : A Complementary Metal-Oxide Semiconductor Digitally Programmable Current Conveyor, International Journal o Circuit Theory and Applications 4 No. (23), 69 8, DOI:.2/cta.786. [7] BIOLEK, D. LAHIRI, A. JAIKLA, W. SIRIPRUCHYA- NUN, M. BAJER, J. : Realisation o Electronically Tunable Voltage-Mode/Current-Mode Quadrature Sinusoidal Oscillator using ZC-CG-CDBA, Microelectronics Journal 42 No. (2), [8] SOULITIS, G. PSYCHALINOS, C. : Electronically Controlled Multiphase Sinusoidal Oscillators using Current Ampliiers, International Journal o Circuit Theory and Applications 37 No. (29), [9] HERENCSAR, N. LAHIRI, A. VRBA, K. KOTON, J. : An Electronically Tunable Current-Mode Quadrature Oscillator using PCAs, Int. Journal o Electronics 99 No. 5 (2), 69 62, DOI:.8/ [] SOTNER, R. LAHIRI, A. KARTCI, A. HERENCSAR, N JERABEK, J. VRBA, K. : Design o Novel Precise Quadrature Oscillators Employing ECCIIs with Electronic Control, Advances in Electrical and Computer Engineering 3 No. 2 (23), [] SOTNER, R. HERENCSAR, N. JERABEK, J. KOTON, J. DOSTAL, T. VRBA, K. : Electronically Controlled Oscillator with Linear Frequency Adjusting or Four-Phase or Dierential Quadrature Output Signal Generation, International Journal o Circuit Theory and Applications, 42 No. 2 (24), [2] SOTNER, R, HRUBOS, Z. HERENCSAR, N. JERABEK, J. DOSTAL, T. : Precise Electronically Adjustable Oscillator

8 Journal o ELECTRICAL ENGINEERING 67, NO, 26 9 Suitable or Quadrature Signal Generation Employing Active Elements with Current and Voltage Gain Control, Circuits Systems and Signal Processing 33 No. (24), 35. [3] MINAEI, S. SAYIN, O. K. KUNTMAN, H. : A New CMOS Electronically Tunable Current Conveyor and its Application to Current-Mode Filters, IEEE Trans. on Circuits and Systems - I 53 No. 7 (26), [4] SIRIPRICHYANUN, M. JAIKLA, W. : Current Controlled Current Conveyor Transconductance Ampliier (CCCCTA): a Building Block or Analog Signal Processing, Electrical Engineering Springer 9 No. 6 (28), [5] KUMNGERN, M. JUNNAPIYA, S. A. : Sinusoidal Oscillator using Translinear Current Conveyors, Proceedings o Asia Paciic Conerence on Circuits and Systems (APPCAS 2), Malaysia, Kuala Lumpur, 2, pp , DOI:.9/APCCAS [6] JAIKLA, W. 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LAHIRI, A. : Single GCFDITA and Grounded Passive Elements based General Topology or Analog Signal Processing Applications, Proceedings o the th International Conerence on Networks - ICN 22, Saint Gilles, Reunion Island, 22, pp [26] SOTNER, R. JERABEK, J. SEVCIK, B. DOSTAL, T. VRBA, K. : Novel Solution o Notch/All-Pass Filter with Special Electronic Adjusting o Attenuation in the Stop Band, Elektronika Ir Elektrotechnika 7 No. 7 (2), [27] SOTNER, R. JERABEK, J. PETRZELA, J. VRBA, K. DOSTÁL, T. : Design o Fully Adjustable Solution o Band-Reject/All-Pass Filter Transer Function using Signal Flow Graph Approach, In Proceedings o the 24th International Conerence Radioelektronika 24, pp [28] SOTNER, R. JERABEK, J. HERENCSAR, N. PROKOP, R. VRBA, K. DOSTAL, T. : Resistor-Less First-Order Filter Design with Electronical Reconiguration o its Transer Function, Proceedings o the 24th International Conerence Radioelektronika 24, 24, pp [29] SOTNER, R. HERENCSAR, N. JERABEK, J. PROKOP, R. KARTCI, A. DOSTAL, T. VRBA, K. : Z-Copy Controlled-Gain Voltage Dierencing Current Conveyor: Advanced Possibilities in Direct Electronic Control o First-Order Filter, Elektronika Ir Elektrotechnika 2 No. 6 (24), [3] HERENCSAR, N. KOTON, J. LATTENBERG, I. VRBA, K. : Signal-Flow Graphs or Current-Mode Universal Filter Design using Current Follower Transconductance Ampliiers (CF- TAs), Proc. o Applied Electronics APPEL28, Pilsen, 28, pp [3] BAKER, J. : CMOS Circuit Design, Layout and Simulation, Wiley-IEEE Press, West Sussex, 28. [32] ELDBIB, I. MUSIL, V. : Sel-Cascoded Current Controlled CCII Based Tunable Band Pass Filter, Proc. 8th Int. Con. Radioelektronika, Praha, 28, pp. 4. [33] MOSIS Parametric Test Results o TSMC LO EPI SCN8 Technology, tp://tp.isi.edu/pub/mosis/vendors/tsmc-8/ t44e lo epi-params.txt Available on-line, cited [34] SURAKAMPONTORN, W. KUMWACHARA, K. : CMOS- Based Electronically Tunable Current Conveyor, Electronics Letters 4 No. 28 (992), 36 37, DOI:.49/el: [35] Intersil (Elantec) EL282 CN Current-Mode Multiplier (datasheet),. [36] Texas Instruments. VCA8: High Gain Adjust Range, Wideband, variable gain ampliier, 23 (last modiied 2/2), 3 p. [37] Analog Devices. AD83 High Speed, Video Dierence Ampliier (datasheet), data sheets/ad83.pd 2 (Rev. C, 3/2), 2 p. [38] Current-mode our-quadrant multiplier EL 483 (datasheet), 995, 6 p. [39] Texas Instruments. OPA66 Wide bandwidth operational transconductance ampliier and buer (datasheet), www: 2, 2 p. [4] Texas Instruments. OPA86 Wide-bandwidth, operational transconductance ampliier (OTA) and buer (datasheet), www: 28, 33 p. [4] SOTNER, R. KARTCI, A. JERABEK, J. HERENCSAR, N. DOSTAL, T. VRBA, K. : An Additional Approach to Model Current Followers and Ampliiers with Electronically Controllable Parameters rom Commercially Available ICs, Measurement Science Review 2 No. 6 (22), Received 28 December 24 Roman Šotner was born in Znojmo, Czech Republic, in 983. He received the PhD degree in Electrical Engineering in 22 rom the Brno University o Technology, MSc degree in 28andBScdegreein26. Currently,heisaresearchworker at the Department o Radio electronics, Faculty o Electrical Engineering and Communication, Brno University o Technology, Brno, Czech Republic. His interests are analogue circuits (active ilters, oscillators, audio, etc), circuits in the current mode, circuits with direct electronic controlling possibilities especially and computer simulation. Jan Jeřábek was born in Bruntal, Czech Republic, in 982. He received the PhD degree in Electrical Engineering in 2 rom the Brno University o Technology, Czech Republic. He is currently assistant proessor at the Department o Telecommunications, Faculty o Electrical Engineering and

9 2 R. Sotner et al: FIRST-ORDER TRANSFER SECTIONS WITH RECONNECTION-LESS ELECTRONICALLY... Communication, Brno University o Technology. His research interests are ocused on circuit design and applications o modern active elements such as adjustable current ampliiers and ollowers, transconductance and transimpedance ampliiers. Norbert Herencsar was born in Slovakia, in 982. He received the MSc and PhD degrees in Electronics & Communication and Teleinormatics rom Brno University o Technology, Czech Republic, in 26 and 2, respectively. Since December 25, he is an Associate Proessor at the Department o Telecommunications o Brno University o Technology, Brno, Czech Republic. During September 29-February 2 and February 23-May 23 he was an Erasmus Exchange Student and Visiting Researcher, respectively, with the Department o Electrical and Electronic Engineering, Bogazici University, Istanbul, Turkey. During January 24 April 24 he was a Visiting Researcher with the Department o Electronics and Communications Engineering, Dogus University, Istanbul, Turkey. His research interests include analog ilters, current-, voltage- and mixed-mode circuits, new active elements and their circuit applications, low transistor count circuits, MOSonly circuits, oscillators, and inductor simulators. He is an author or co-author o 56 research articles published in SCI-E peer-reviewed international journals, 24 articles published in other journals, and 89 papers published in proceedings o international conerences. Since 2, he is Deputy-Chair o the International Conerence on Telecommunications and Signal Processing (TSP). Since 22, is Co-editor o the International Journal o Advances in Telecommunications, Electrotechnics, Signals and Systems. Since 24, he is Associate Editor o the Journal o Circuits, Systems and Computers (JCSC). Dr. Herencsar is Senior Member o the IEEE, IACSIT, and IRED, and Member o the IAENG, ACEEE, and RS. Since 25, he serves as IEEE Czechoslovakia Section SP/CAS/COM Joint Chapter Chair as well as Membership Development Oicer. Roman Prokop was born in Velké Meziříčí in 97. He received the MSc and PhD degrees in Electrical Engineering rom the Brno University o Technology, Czech Republic, in 995 and 29, respectively. He is currently working as Assistant at the Dept. o Microelectronics, Brno University o Technology. His research is in the ield o integrated circuit design, where his interests include modern innovative analog circuits, current mode circuits, analog signal processing and digitally tunable analog circuits. Abhirup Lahiri received Bachelor o Engineering (BE) degree with the highest honors rom the Division o Electronics and Communications, Netaji Subhas Institute o Technology (erstwhile, Delhi Institute o Technology), University o Delhi, India. His past research works include design o compact analog circuit solutions using novel voltage-mode and currentmode active elements. His current research interests include low-power and low-voltage analog circuit design and precision voltage and current reerence generation. He has authored/coauthored more than thirty international journal/conerence papers (including iteen SCI/SCI-E publications) and has acted as a reviewer (by editor s invitation) or numerous international journals and conerences o repute. He served as a program committee member or the International Conerence on Telecommunications and Signal Processing (TSP). He is an editorial board member o Radioengineering Journal or the years His biography is included in Marquis Who s Who in the World 2- (28th Edition). Tomáš Dostál born in 943, received his PhD (976) and DrSc degree (989). He was with the University o Deense Brno ( and ), with the Military Technical College Baghdad (978-98), with the Brno University o Technology (984-28) and with the European Polytechnic Institute (28-29). Since 29 he has been with the College o Polytechnics, Jihlava as Proessor o Electronics. His interests are in circuit theory, analog ilters, switched capacitor networks and circuits in the current mode. Kamil Vrba received the PhD degree in Electrical Engineering in 976, and the Pro degree in 997, both rom the Technical University o Brno. Since 99 he has been Head o the Dept. o Telecommunications, Faculty o Electrical Engineering and Computer Science, Brno University o Technology, Brno, Czech Republic. His research work is concentrated on problems concerned with accuracy o analog circuits and mutual conversion o analog and digital signals. In cooperation with AMI Semiconductor Czech, Ltd. (now ON Semiconductor Czech Republic, Ltd.) he has developed number o novel active unction blocks or analog signal processing such as universal current conveyor (UCC), universal voltage conveyor (UVC), programmable current ampliier (PCA), and others. He is an author or co-author o more than 65 research articles published in international journals or conerence proceedings. Proessor Vrba is a Member o IEEE, IEICE, and Associate Member o IET.