Schmitt Trigger with Controllable Hysteresis Using Current Conveyors

Transcription

1 International Journal Advances Telecommunications, Electrotechnics, Signals and Systems Vol., No. (0) Schmitt Trigger Controllable Hysteres Usg Current Conveyors Jiri Murec and Jaroslav Kon Abstract Active elements workg current or mixed mode are still attractive for design analog functional blocks. current conveyor (CC) was defed already 968. Th paper deals s usg second generation current conveyor. basically a pulse circuit. In se circuits, maximum rate change output voltage required durg switchg from one state anor. In s operational amplifiers switchg time given by slew rate operational amplifier used, which not o high. If a current conveyor used, time switchg gets shorter. capable operate at a higher bands and if it used, for example, converters, a higher operatg can reached. connection an vertg and a non-vertg adjustable shown as a practical implementation. Usg A844, results experimental measurements are presented that confirm oretical assumptions and results computer simulation. Keywords Current conveyor, analog circuit design,. I. INTROUCTION current conveyors as active elements are known sce 968 [], when Smith and Sedra presented first-generation current conveyor (CCI). Later on second- and thirdgeneration current conveyors have en designed [], [3]. se elements are now advantage used applications, where wide bandwidth or current output response necessary. Nowadays, different types current conveyors are descrid that are mostly based on CCII, e.g. current controlled CC (CCCII) [7], differential voltage CC (VCC) [8], or electronically tunable CC (ECCII) [9], [0]. application possibilities current conveyors are mostly presented on lear circuit design, e.g. filters [4] [7] or immittace simulars [8] []. However, CCII can used implement or functional blocks, such as Schmitt trigger circuit, by creatg a regenerative feedback that takes part output voltage from termal and applies it termal active element [], [3]. Schmitt Triggers based on or active elements such as Current Through Transconductance Amplifier (CTTA) or Current ifferencg Transconductance Amplifier (CTA) can found e.g. [4], [5]. In th paper we use simple second-generation current conveyors implement Schmitt trigger vertg and non-vertg loop. First basic circuit pology descrid that subsequently supplemented by and digital- J. Murec and J. Kon are epartment Telecommunications, Brno University Technology, Purkynova 8, 6 00 Brno, Czech Republic. Correspondg author: murec@feec.vutbr.cz. Manuscript received July 5, 0; reved Septemr 9, 0. analog converter reference put enablg digital control value Schmitt trigger. havior proposed circuit analyzed both by SPICE simulations and experimental measurements showg performance Schmitt trigger. II. SECON-GENERATION CURRENT CONVEOR AN ITS IMPLEMENTATION Generally, second-generation current conveyors, termal only a voltage termal havg fite put impedance ory. port current put and current transfer from port port zero, from it unity. A three-port volved here (see ), matrix representation which given by relations: V I I I V V. () Its advantageous properties and application possibilities have grown development circuits and systems current mode. Second-generation current conveyors have come feature promently circuit structures some commercially manufactured circuits. A844 circuit a transimpedance amplifier (Analog evices). In its ternal structure re a second-generation current conveyor. A high-impedance outlet important here, which used as port z conveyor. ternal connection circuit shown (, schematic symbol A844 circuit PSpice program, and ideal model (c). It evident from equivalent circuit connection that its ternal connection consts two voltage followers and one current follower. Current flows via put restance R IN ( put restance low-impedance termal ca. 50 Ω). Th current detected by current follower and transferred transimpedance termal. current passage through so-called transimpedance produces a voltage, which conveyed compensation termal. On th termal output current I current conveyor obtaed o. For sake load separation. I V I V Schematic symbol second-generation current conveyor I V doi: 0.60/ijates.vi.9 6

2 International Journal Advances Telecommunications, Electrotechnics, Signals and Systems Vol., No. (0) I V a voltage follower I cluded on voltage output Itransimpedance amplifier. However, case current conveyor Vvoltage output not made use. transimpedance models impedance output termal and formed by a parallel combation restance (its magnitude ca. 3 MΩ) and capacitance C t (cca. 4.5 pf). output impedance 5 transimpedance termal th current source high. 3 output circuits s are nature pulse I circuits and IN 6 thus a maximum rate change output R IN C t voltage usually required comparon. Th parameter has a direct fluence on switchg time. In classical operational amplifier switchg time given by slewrate operational amplifier used. In s current conveyors switchg time substantially shorter. V III. HSTERESIS COMPARATOR WITH Similarly as [], transimpedance amplifiers A844 [6] cludg were used implement. schematic diagram a implemented usg two conveyors shown 3. From connection non-vertg operational amplifier equivalent connection nonvertg or vertg can derived. connection given 3 coms two possibilities. circuit part contag A current conveyor I represents I non-vertg while Ipart V contag B current conveyor performs V function an vertg. V n output voltage V output non-vertg I V 3 I V 3 R IN I V 5 ( C t U V NN IN 6 IN R IN C t - C 5 4 A844/A V- (c) 6 6. ( Internal connection circuit A844 [6], symbol circuit A844 PSpice program, (c) idealized model circuit A V IN I A R 4 B I A I B R 3 R R V V Non-vertg and vertg two s, and output voltage V output vertg. To descri activity and determe values positive comparon voltage V P and negative comparon voltage V N from 3 we will start from knowledge A844 circuit as given above. In th case most important parameter magnitude transimpedance formed by a parallel connection restance and capacitance C t. se elements form impedance output termal. output restance R low-impedance termal also needs taken consideration. Consider that output voltage V can acquire values V SAT or V SAT, output voltage V always acquirg opposite values, i.e. V SAT and V SAT. outputs V and V are mutually complementary. Consider that output voltage V conveyor B has a maximum positive level, i.e. V V SAT, which case voltage V P on port current conveyor B given by relation: V P V SAT R R R V SAT β. () If on contrary re on output conveyor B a mimum negative level, V V SAT, n voltage on port th conveyor : V N V SAT R R R V SAT β. (3) By defition current conveyor it holds that V V, so that voltage on port will repeated also on port B. refore, current flowg termal can expressed as: I V IN V SATβ R R 4. (4) From conveyor defition it furr follows that output current conveyor A I A I, and output current conveyor B I B I. output voltage 7

3 International Journal Advances Telecommunications, Electrotechnics, Signals and Systems Vol., No. (0) conveyor A n given by relation: V A V V IN V SAT β R R 4 and output voltage conveyor B : V B V V IN V SAT β R R 4 s C t (5) s C t, (6) where s jω, whereas ω angular. Simplified relations can obtaed form V A V R R 4 (V IN V SAT β), (7) V B V (V IN V SAT β), (8) R R 4 where negative sign and positive sign parenses denote state output voltages V and V. If V V SAT, n V V SAT, and if V V SAT n V V SAT. After switchg conveyor outputs values V V SAT and V V SAT put voltage V IN must drop low value V SAT β. defed as difference tween positive and negative comparon level put voltage and thus given by relation: V. IGITAL CONTROL OF HSTERESIS AN EPERIMENTAL MEASUREMENTS For digital control magnitude connection cludg a was proposed as given 5. itial basic connection given 3 was complemented a multiplier digital--analog converter A7533 [], operational amplifier LM74 (which connected as a voltage follower), and a third current conveyor A844. Voltage from divider R -R conveyed multiplier, where it multiplied by value a 0-bit put word, which sets magnitude. refore, it necessary multiply relations (), (3) and (9) by value. value expresses bary fraction value 0-bit digital put word AC; examples calculatg for some combations are given Table I. In connection implemented, can set an terval h 0 V h.5 V, dependence on set combation 0-bit digital word. measured s for control word given 6. For th value numr maximum value obtaed, h.5 V. For shown 7 while for it shown h V P ( V N ) V SAT β ( V SAT β) βv SAT. (9) IV. COMPUTER SIMULATION OF HSTERESIS COMPARATOR WITH ( operation from 3 was tested computer simulation. In MicroCap simulation program model A844A circuit will used. circuit parameters set for simulation were: supply voltage V CC ±5 V, saturation voltage V SAT 0 V, restance values chosen are R R 0 kω, consequently β 0.5, R 3 0 kω, and R 4 kω. calculated value comparon voltage V P 5 V and n h 0. For chosen V IN 0 V output current magnitudes two current conveyors are I A 4.5 ma and I B 4.5 ma. Simulation results are given for non-vertg 4(, and for vertg 4. Arrowheads s follow direction change 4. Waveform charactertics non- b) put voltage V IN. As can seen, circuit performs 4. Waveform vertg, charactertics b) vertg nonvertg, expected function. circuit part contag B b) vertg fulfills function vertg, part A performs function non-vertg 4. ( non-vertg, vertg charactertic. from 3 4 Computer and controlled 4 Computer and controlled For digital control magnitude connection cludg a For was digital proposed control as given magnitude 5. itial basic connection connection given cludg 3 a was complemented was proposed as given a multiplier 5. digital--analog itial basic connection converter given A7533JN, 3 was complemented a multiplier digital--analog converter 8 A7533JN,

4 International Journal Advances Telecommunications, Electrotechnics, Signals and Systems Vol., No. (0) TABLE I B INAR FRACTION REPRESENTATION OF SOME COMBINATIONS OF 0- BIT AC INPUT IGITAL INPUT B INAR FRACTION VALUE igital put (MSB LSB) Bary fraction value 03/04 53/04 5/04 5/04 /04 0/04 A IA B schematic s variable VIN R3 V ( IB R V 7. Hysteres loop for , nonb) vertg ection shown 5 re vertg output put and non-vertg output voltage R4 es on Ioutput. Jumpers are used for choosg R digital put word ; fal implementation, electronic A844 LM74 veform for _ control5word given A7533 _ 0k e numr maximum value... r shown 7 while b) scillogram shown 8. value schematic hs variable 7. Hysteres loop for , non 5. esign 7. Hysteres , fornon-vertg 7. Hysteres loop , ( non-vertg by parameter cursors left botm loop for b) vertg b) vertg vertg 5. esign schematic. right botm s valueconnection Vvariable outsatshown In 5 re vertg output 8. Hysteres voltage on output and non-vertg output voltage loop for , nonb) vertg digitally controlled on output. Jumpers are used for choosg combation 0-bit digital put word ; fal implementation, electronic testg put has a susoidal frequ control reckoned. oscilloscopic for control word given With creasg 6. For th value numr maximum value put magnit changes. obtaed, h.5v. For shown 7 b) while output vertg c f 5.5 khzh and set given for shown 8. value 7. Hysteres loop for , non-vertg left for put f 650 Th s given by parameter cursors botm b) vertg s given 8b. For a while parameter ( value V ( b) right botm outsat. b) h 5mV but actual hyster oop for, non-vertg Hysteres loop for , non 8. Hysteres loop for , 8. non-vertg put creases, loop gets m b) vertg b) vertg b) vertg namic properties current conveyors come fully sho g, testg overshootg can observed on put susoidal wavef freque testg put has a susoidal f has.aprecion, on showg util A844AN. put magnit With With creasg put creasg magnitude value changes. vertg c changes. output vertg at output put f 5.5 khz and set given f 5.5 khz and set given 9a while 9b for put f 650 Th for put f 650 two s can s givenword 8b. For a b) For given 8b. above b)value put s h 5mV but 6. Hysteres loop, non-vertg loop h 5mV but actual value 300mV. If actual hystere 8. for Hysteres for , non-vertg 6. Hysteres loop for, ( non-vertg 8. Hysteres loop for , ( non-vertg put creases, loop gets m b) vertg put creases, loop gets more extended and dyb) vertg vertg vertg namic properties current conveyors come fully sho namic properties current conveyors come fully shown. At time switchg, overshootg can observed on wavef g, testg observed on a consider puvershootg has a can susoidal s. f Th.has util 8. value h given output atprecion, put on precion, showg vertg onutilizable bandshowg A844AN. by parameter cursors left botm 5.5 khz and set given 9( while A844AN. With creasg put magnitude value while parameter changes. right botm 9 for put 650 output vertg at put value V SAT. testg put was a susoidal two s can s f 5.5 khz and set given 9a while 9b. given 8. For above value put word for put f 650 two s can With creasg put mag- h 5 mv but actual s given 8b. For above value put word nitude value changes. s value 300 mv. If put creases, h 5mV but actual value 300mV. If put creases, loop gets more extended and dynamic properties current conveyors come fully shown. At time switchg, overshootg can observed on s. Th has a consider9 on precion, showg utilizable band A844AN.

5 International Journal Advances Telecommunications, Electrotechnics, Signals and Systems Vol., No. (0) 9. Hysteres loop vertg for , f 5.5kHz b) f 650kHz In connection implemented, can set an terval h 0V h.5v, dependence on set combation 0-bit digital word. 3 Conclusion ( f vertg 9. Hysteres for loop vertg , for , ( tegrated astable multivibrar based on a sgle CCII, Proc. f 5.5 paper khz presents f 650 solution khz 5.5kHz b) f 650kHz a voltage Research Mcroelectronics current conveyors and Electronics Conference, pp ,. A oretical analys and computer simulation are 007. performed and a digitally [4] P. Silapan and M. Siripruchyanun, A Simple Current-mode Schmitt ection implemented, controlled loop gets vertg more extended can and set and non-vertg an dynamic terval properties proposed. Trigger Employg Only Sgle MO-CTTA, has Proc. 6th Int. Conf. some pulse circuit elements and refore a maximum rate Electrical output Engeerg/Electronics, voltage change Computer, Telecommunications and dependence current on conveyors set combation come 0-bit fully digital shown. word At time Information Technology - ECTI-CON, Vol. 0, pp , 009. switchg, usually required. overshootg Measurg can on an observed experimental on specimen [5] P. Silapan shows and M. results Siripruchyanun, obtaed. Fully and electronically controllable th controlled current-mode. Schmitt triggers employg only sgle MO- s. Somewhat Th hastter a considerable results were effectexpected on precion, showg Examg utilizable causes will band subject furr vestigation. design CCCTA and ir applications, Analog Integr Circ Sig Process, doi: 0.007/s , values Vol. 68, h measured for three chosen combations [6], atasheet i.e. full A844: extent 60 MHz h, half 000V/µs Monolithic Op Amp, Analog pp. -8, 0. A844. evices, Rev. F extent h, and least value h, were calculated values. deviation from VI. se CONCLUSION values ca. 3% for dividual values applications. based In on a new connection current controlled conveyor, IEEE Trans. [7] A. Fabre, O. Saaid, F. Wiest, and C. Baucheron, High paper given, presents re evidently solution a drop a voltage voltage, obviously due Circuits Syst.-I, A7533JN Vol. 43, No., multiplier. Measurg conveyors. Acurrent oretical conveyors out analys multiplier and did not conveyor exhibit and its th applications, error. Thus IEE Proc. Circuits, evices, Systems, Vol. pp. 8-90, 996. [8] H.O. Elwan and A.M. Soliman, Novel CMOS differential voltage current lution a voltage current s and computer good simulation functionality were are performed and and a digitally a was controlled verified and 44, No. advantage 3, pp , 997. current n-vertg vertg mode and was non-vertg shown. proposed. Furr work has will en focus has proposed. [9] S. Maei, O.K. Say, and H. Kuntman, A new CMOS electronically on obtag a tunable higher current operatg conveyor and. its application current-mode filters, IEEE and refore a maximum has rate some pulse output circuit voltage elements change and refore Trans. Circuits Systems I, Vol. 53, No. 7, p , 006. on an experimental a maximum rate specimen output shows voltage change results obtaed. usually required. [0] W. Surakamponrn and K. Kumwachara, CMOS-based electronically ere expected Measurg on design an experimental th controlled specimen. shows results tunable current conveyor, Electronics Letters, Vol. 8, No. 4, pp , 99. subject obtaed. furr values vestigation. h measured values for three hyse chosen combations, i.e., full i.e. extent full extent h, half h, half extent h, and evices, Rec. C, 007. chosen [] atasheet A7533: CMOS low cost 0-bit multiplyg AC, Analog alue h, were least value h, were calculated values. calculated values. de ca. 3% for dividual values. In connection lectures and leads exerce for subject Analog technique and Jiri Murec MSc. (985), Ph.. (99), Ass. Pr. (007) Brno University Technology, ept. Teleformatics, Czech Republic. He deviation from se values was cca. 3% for dividual values. In connection given, re evidently a drop lectures course igital Signal Processg. H research terest drop voltage, obviously due A7533JN multirar out multiplier out did not multiplier exhibit th diderror. not exhibit Thus workg both voltage and current mode. Now he terested general- voltage, obviously due A7533 multiplier. Measurg focused on area analog technique, converters, especially on converters th error. omparar Thus was verified good functionality and advantage current ization sensitivity analys transfer functions. Th used for was verified comparon newly developed applications. In latest he also cooperates ork will and focus on advantage obtag a higher current operatg mode was. shown. Furr a numr companies on implementation fundamental research results practice. work will focus on obtag a higher operatg. REFERENCES [] K. C. Smith and A. Smith, Current Conveyor: a New Circuit Buildg Block, IEEE Proc., Vol. 56, pp , 968. [] A. Sedra and K. C. Smith, A second-generation current conveyor and its application, IEEE Trans. Circuit ory, Vol. 7, pp. 3-34, 970. [3] A. Fabre, Third-generation current conveyor: a new helpful active element, Electronics Letters, Vol. 3, No. 5, pp , 995. [4] M. Sagbas, K. Fidanboylu, and M. C. Bayram, Triple-put Sgleoutput Voltage-mode Multifunction Filter Usg Only Two Current Conveyors, Trans. Engeerg, Computg and Technology, Vol. 4, pp , 005. [5] S. Maei, O. K. Say, and H. Kuntman, A new CMOS electronically tunable current conveyor and its application current-mode filters, Tran. Circuits and Systems I, Vol. 53, pp , 006. [6] S. A. Mahmoud, M. A. Hashiesh, and A. M. Soliman, igitally controlled fully differential current conveyor: CMOS realization and applications, Proc. IEEE Int. Symp. Circuits and Systems - ISCAS, Vol., pp. 6-65, 005. [7] P. Prommee, M. Somdunyakanok, and S. Toomsawasdi, CMOS-based current-controlled CC and its applications, Proc. IEEE Int. Symp. Circuits and Systems - ISCAS, pp , 00. [8] S. Ozoguz and A. Acar, On realization floatg immittance function simulars usg current conveyors, Int. J. Electronics, Vol. 85, No. 4, pp , 998. [9] U. Cam, O. Cicekoglu, and H. Kuntman, Universal series and parallel immittance simulars usg four termals floatg nullors, Analog Integrated Circuit and Signal Processg, Vol. 5, No., pp. 5966, 000. [0] E. Arslan, B. Met, C. Cakir, O. Cicekoglu, A novel grounded lossless ductance simular CCI, Proc. Int. II. Turkh Symposium on Artificial Inteligence and Neural Networks, 003. [] E. uce, S. Maei, and O. Cicekoglu, A novel grounded ducr realization usg a mimum numr active and passive components, ETRI Journal, Vol. 7, pp , 005. [] S. Bima, A. Khan, S. Roy, and K. ey, Programmable Hysteres Comparar Circuits usg Current Conveyor, J. Instrum. Soc. India, No. 3, pp.85-93, 997. [3] S. el Re, A. e Marcell, G. Ferri, and V. Srnelli, Low voltage Jaroslav Kon received M.Sc. an Ph.. degree electrical engeerg from Brno University Technology, Czech Republic, 006 and 009, respectively. He currently an Asstant Pressor at epartment Telecommunications Faculty Electrical Engeerg and Communication Brno University Technology, Czech Republic. H current research focused on lear and non-lear circuit designg methods current or voltage conveyors, and current active elements. He an author or co-author about 85 research articles publhed ternational journals or conference proceedgs. r. Kon a Memr IEEE and IACSIT. 30