A single MO-CFTA based electronically/temperature insensitive current-mode half-wave and full-wave rectifiers

THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 11 |NUMBER: 4 |2013 |SEPTEMBER A Single MO-CFTA Based Electronically/Temperature Insensitive Current-mode Half-wave and Full-wave Rectifiers Weerapon KONGNUN, Phamorn SILAPAN Electric and Industrial Program, Faculty of Industrial Technology, Uttaradit Rajabhat University, Muang, 530 00 Uttaradit, Thailand weerapon.k[email protected], [email protected] Abstract. The article presents a current-mode fullwave rectifier employing multiple output current follower transconductance amplifier (MO-CFTA). The both circuits description is very simple, it merely comprises only single MO-CFTA, without external passive element. In addition, the magnitude and direction of output currents can be controlled via electronically method. Furthermore, the outputs are independent of the thermal voltage (VT). The performances of the proposed circuits are investigated through PSpice. They show that the proposed circuits can function as a current-mode precision half-wave and full-wave rectifiers where input current range from 0 µA to 514 µA and -518 µA to 518 µA, respectively. They can be achieved at ±2V power supplies. The maximum power consumption is 3,01 mW. Keywords Current-mode, MO-CFTA, rectifier. 1. Introduction A rectifier has been found widely useful in signal processing circuits, such as a signal polarity detector, a peak signal detector, an RMS to DC converter, an amplitude demodulation circuit, and an automatic gain control system [1], [2]. Basically, an op-amp and diode are used to design a voltage-mode precision rectifier [3], its output signal confronts a zero crossing distortion due to characteristic of the diode [4]. Thus, novel precision rectifiers are design without a diode [5]. In addition, the precision rectifiers are modified to use high performance active elements to achieve wider frequency response such as current conveyor [6] and current feedback operational amplifier [7]. However, these circuits use many active and passive elements. When they are fabricated in IC, it affects to have more chip area. Furthermore, they are lack of electronically adjustment. There has been much effort to reduce the supply voltage of analog systems since the last two decades. This is due to the command for portable and batterypowered equipments. Since a low-voltage operating circuit becomes necessary, the current–mode technique is ideally suited for this purpose. Presently, there is a growing interest in synthesizing current-mode circuits because of more their potential advantages such as larger dynamic range, higher signal bandwidth, greater linearity, simpler circuitry, and lower power consumption [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19]. In 2008, a reported active element, namely current follower transconductance amplifier (CTFA) [20], [21], seems to be a versatile component in the realization of a class of analog signal processing circuits. It is really current-mode element whose input and output signals are currents. In addition, output current of CFTA can be electronically adjusted. Furthermore, it can offer advantageous features such as high-slew rate, high speed, wide bandwidth and simple implementation. The purpose of this paper is to introduce MOCFTA based current-mode half-wave and full-wave rectifiers. The features of the proposed both circuits are that; output gain can be adjusted via input bias current; magnitude of the output signal is temperatureinsensitive; the proposed circuit consists of only single MO-CFTA and without passive element, which is convenient to fabricate in integrated circuit architecture. The PSpice simulation and experimental results are also shown, which are in correspondence with the theoretical analysis. c 2013 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 275 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 11 |NUMBER: 4 |2013 |SEPTEMBER 2. Circuit Configulation 2.1. Basic Concept of MO-CFTA This section describes the operation of MO-CFTA, its symbol and equivalent circuit are display in Fig. 1(a) and Fig. 1(b), respectively. In the ideal case, the voltage and current relationships of MO-CCTA are shown in (1),       Vf Iz Ix1 Ix2 I−x       =       0 0 0 0 0 1 0 0 0 0 0gm1000 0gm2000 0gm3000             If Vz Vx1 Vx2 V−x       ,(1) where gm1=IB1 2VT , gm2=IB2 2VT and gm3=IB3 2VT .(2) gm1, gm2and gm3are the transconductances of the MO-CFTA at x1, x2, x3terminals, respectively VTis the thermal voltage, its value is about 26 mV at 27 ◦C. Fig. 1: MO-CFTA a) Schematic symbol, b) Equivalent circuit. 2.2. The Current-Mode Half-Wave Rectifier This section is explained the operating of the half-wave rectifier, it is shown in Fig. 2. It can be seen that it consists of single only MO-CFTA without passive element. From MO-CFTA properties, the Izand Vz can be found to be: Iz=If=IC=I−x,(3) and Vz=I−x gm3 =IC gm3 .(4) Cosequently, the Ix1can be written as: Ix1=gm1Vz=I−x gm3 =gm1IC gm3 .(5) From the half-wave rectifier as demonstrated in Fig. 2, IB1= Iin. Hence, gm1= Iin/2VT, Eq. (5) can be modified to be: Ix1=∈   IinIC IB3 if Iin >0 0if Iin <0 .(6) Fig. 2: Circuit diagram of current-mode half-wave rectifier. 2.3. The Current-Mode Full-Wave Rectifier The proposed full-wave rectifier using MO-CFTA is display in Fig. 3, where IB1, IB2and IB3are current bias currents of the MO-CFTA, respectively. By routine analysis circuit in Fig. 3 and using the properties of MO-CFTA. The output current at z terminal of MOCFTA is obtained in: Iz=If=IC,(7) and Iz=I−x.(8) c 2013 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 276 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 11 |NUMBER: 4 |2013 |SEPTEMBER Then, the output voltage at z terminal (Vz) of MOCFTA can be found to be: Vz=I−x gm3 =IC gm3 .(9) Subsequently, the output current at x1 and x2 terminals (Ix1and Ix2) can be expressed to be: Ix1=gm1Vz=gm1IC gm3 ,(10) and Ix2=gm2Vz=−gm2IC gm3 .(11) From Fig. 2, it is found that Iin and -Iin are equal to IB1and IB2respectively. Then, gm1= Iin / 2VT, gm2 = -Iin / 2VTand gm3= -IB3/ 2VT. From MO-CFTA properties, the values of currents bias only are positive. Thus, Ix1and Ix2can be rewritten to be: Ix1=∈   IinIC IB3 if Iin >0 0if Iin <0 ,(12) and Ix2=∈   0if Iin >0 IinIC IB3 if Iin <0.(13) From Eq. (12) and Eq. (9), the output current Iout can be found to be: Iout =Ix1+Ix2=|Iin |IC IB3 .(14) From Eq. (6) and Eq. (14), it can be seen that the amplitude of the output current can be controlled by IB3and IC, the polarity of the output signal can be electronically tune by IC. Furthermore, in the ideal case, the current output is temperature-insensitive. Fig. 3: Circuit diagram of current-mode full-wave rectifier. 2.4. Non-Ideal Case In non-ideal case, the MO-CFTA can be characterized by:       Vf Iz Ix1 Ix2 I−x       =       0 0 0 0 0 α0 0 0 0 0γgm1000 0γgm2000 0γgm3000             If Vz Vx1 Vx2 V−x       ,(15) where αand γare transferred error values, these values can be deviated from one. In the case of non-ideal and reanalyzing the proposed half-wave and full-wave rectifiers in Fig. 2 and Fig. 3, respectively, they yield the output currents as: Ix1=∈   αIinIC IB3 if Iin >0 0if Iin <0 ,(16) and Iout =Ix1+Ix2=α|Iin |IC IB3 .(17) From small-signal analysis of MO-CFTA, it can be found that αcan be express as: α=gm6gm8gm13 gm6gm13(gm8+gm10).(18) If these error factors are close to unity, the deviations of the output levels in Eq. (16) and Eq. (17) can be neglected. Practically, the α, and γoriginate from intrinsic resistances and stray capacitances in the MO-CFTA. These errors affect the sensitivity to temperature and high frequency response of the proposed circuits. Then the MO-CFTA should be carefully designed to achieve these errors as low as possible. 2.5. Non-Linear Case This section expands the proposed rectifiers operating in non-linear case. From Eq. (1) and Eq. (2), the currents at x1, x2and x3terminals can be found to be IB1Vz 2VT ,IB2Vz 2VT and IB3Vz 2VT , respectively. These are the first approximation of Taylor’s series, it can be describe as: tanhx=x−1 3x3+2 15x5−17 315x7+... . (19) Actually, Ix1,Ix2and Ix3can be express to be: Ix1=IB1tanh Vz 2VT,(20) Ix2=IB2tanh Vz 2VT,(21) c 2013 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 277 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 11 |NUMBER: 4 |2013 |SEPTEMBER and Ix3=IB3tanh Vz 2VT.(22) Subsequently, the output current of the half-wave rectifiers can be obtained by: Iout =   Iintanh IC IB3 if Iin >0 0if Iin <0 .(23) Likewise, the amplitude of the full-wave rectifier can be found to be: Ix1=   Iintanh IC IB3 if Iin >0 0if Iin <0 ,(24) Ix2=   0if Iin >0 Iintanh IC IB3 if Iin <0,(25) and Iout =Ix1+Ix2=|Iin |tanh IC IB3 .(26) From Eq. (22) and Eq. (24), it can be clearly seen that the proposed circuits can be used rectifier while perform in non-linear mode. 3. Simulation and Experimental Results The performance of the proposed half-wave and fullwave rectifiers can be proved by simulation and experimental results. Fig. 4: Transistor-level implementation of MO-CFTA. The PSpice simulation program was used for the examinations. The circuit diagram of MO-CFTA is used for simulation, it is display in Fig. 4. The PNP and NPN transistors employed in MO-CFTA were simulated by respectively using the parameters of the PR200N and NR200N bipolar transistors of ALA400 transistor array from AT&T [22] with ±2 V supplies voltages and IAwas set to 100 µA. Figure 4 and Fig. 5 depict DC transfer characteristics of the half-wave and Fig. 5: DC transfer characteristic of the half-wave rectifier. Fig. 6: DC transfer characteristic of the full-wave rectifier. Fig. 7: The simulation results of the half-wave rectifier where IB2= 100 µA, 150 µA and 200 µA. c 2013 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 278 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 11 |NUMBER: 4 |2013 |SEPTEMBER Fig. 8: The simulation results of the full-wave rectifier where IB2= 100 µA, 150 µA and 200 µA. Fig. 9: The current gain where IB3is varied. Fig. 10: The results of output current of the half-wave rectifier for different input frequencies a) 10 kHz b) 100 kHz. full-wave rectifiers, respectively. It can be seen that the proposed circuits offers a wide-range of input current to be both rectifiers. Additionally, its output current direction can be controlled by IC. The simulation results of the both rectifiers, where IB3=100 µA, 150 µA and 200 µA are displayed in Fig. 7 and Fig. 8. From these results, they are confirmed that the output amplitude can be controlled by IB3and IC, respectively. The plot of the current gain relative to the IB3variations is display in Fig. 6. The transient responses of the output current for different input frequencies are also shown in Fig. 10 and Fig. 11. It is concluded that the proposed circuits can operate well for a wide range of frequency; even frequency is up to 100 kHz without disturbing magnitude of the output current. The output signals of the proposed rectifiers relative to temperature variations for 27 ◦C, 50 ◦C and 100 ◦C are respectively shown in Fig. 12. It is clearly observed that the output currents are slightly dependent on the wide temperature variations due to independency of VT, as explained in Section 2.2. Fig. 11: The results of output current of the current-mode fullwave rectifier for different input frequencies a) 10 kHz b) 100 kHz. The deviation values of amplitude of the output currents relative to the temperature variations are demonstrated in Fig. 13. It is found that the maximum absolute deviation of the magnitude of the output current is less than −0,7 %, for temperature variations of 0 - 100 ◦C. These deviations originate from the effect of the intrinsic resistances and stray capacitances of the transistors used in the MO-CFTA, as depicted in Section 2.3. To confirm that the half-wave and full-wave rectifiers can operate practically, they were constructed via using commercial ICs, it is shown in Fig. 14 where it is implemented by using AD844 and LM13700s. In this work, the current follower circuit and OTAs inside the c 2013 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 279 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 11 |NUMBER: 4 |2013 |SEPTEMBER Fig. 12: Output current deviations for different temperature values a) Half-wave rectifier b) Full-wave rectifier. Fig. 13: The output amplitude deviation of the full-wave rectifier due to temperature variations. MO-CFTA can be realized by using two AD844s and LM13700Ns, respectively. Figure 15 and Fig. 16 demonstrate the practical implementation used for experimental inspection of the proposed half-wave and full-wave rectifiers, respectively. Since, the input signal is voltage form, the CFA1-CFA2 of the half-wave rectifier and the CFA1CFA4 of the full-wave rectifier are used to be a V to I converters where both RLis used to be able to measure the output current by an oscilloscope. The experimental results the half-wave and full-wave rectifiers are illustrated in Fig. 17 and Fig. 18, respectively, it Fig. 14: A possible implementation of MO-CFTA employing AD844 and LM13700s. Fig. 15: Practical implementation for experimental inspection of the proposed half-wave rectifier. is insisted that the proposed both rectifiers practically work. 4. Conclusion The new current-mode half-wave ans full-wave rectifier have been presented in this paper. Its advantages are that; the both rectifiers consist of only one MO-CFTA without any passive element; the output amplitude is slightly dependent on temperature variations. Moreover, they can be electronically adjusted by input bias currents. The proposed circuits can operate at high frequency up to several hundred kilohertz range. The results obtained by PSpice simulation found that the maximum power consumption of the proposed circuits are approximately 3,01 mW at ±2 V supply voltages. c 2013 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 280 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 11 |NUMBER: 4 |2013 |SEPTEMBER Fig. 16: Practical implementation for experimental inspection of the proposed full-wave rectifier. Fig. 17: The experimental result of the proposed half-wave rectifier where R1= R2= RL= 1 MΩ, VC= 1 V and IB3= 100 µA. Fig. 18: The experimental result of the proposed full-wave rectifier where R1= R2= R3= RL= 1 MΩ, VC= 10 V and IB3= 10 mA. 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In: The 8th Electrical Engineering/ Electronics, Computer, Telecommunications and Information Technology (ECTI) Association of Thailand - Conference 2011. Phitsanulok: IEEE, 2011, pp. 82–85. ISBN 978-1-4577-0425-3. DOI: 10.1109/ECTICON.2011.5947776. [20] HERENCSAR, N., J. KOTON, I. LATTENBERG and K. VRBA. Signal-flow Graphs for Current-mode Universal Filter Design Using Current Follower Transconductance Amplifiers (CFTAs). In: Proceedings of the Applied Electronics - APPEL’08. Pilsen: IEEE, 2008, pp. 69–72. ISBN 978-80-7043-654-7. [21] BIOLEK, D., R. SENANI, V. BIOKOVA and Z. KOLKA. Active Elements for Analog signal Processing: Classification, Review, and New Proposals. Radioengineering. 2008, vol. 17, no. 4, pp. 15– 32. ISSN 1210-2512. [22] FREY, D. R. Log-domain Filtering: an Approach to Current-mode Filtering. Circuits, Devices and Systems, IEE Proceedings G. 1993, vol. 140, iss. 6, pp. 406–416. ISSN 0956-3768. About Authors Weerapon KONGNUN was born in Uttaradit, Thailand in 1976. He received his B. Eng. major in Instrument Engineering and M. Eng. major in Electrical Engineering from King Mongkut’s Institute of Technology Ladkrabang (KMITL) in 1999 and 2002. Presently, he works with Department of Electrical Computer and Industrial, Faculty of Industrial Technology, Uttaradit Rajabhat University, Uttaradit, Thailand since 2004. His research interests include analog integrated circuit, microcontroller, power electronics and its application. Phamorn SILAPAN was born in Phaitsanulok, Thailand in 1977. He received his B. Eng. degree in electrical engineering from Mahanakorn University of Technology, Thailand in 2002, M. Tech. Ed. in electrical technology and Ph.D. in electrical education c 2013 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 282 THEORETICAL AND APPLIED ELECTRICAL ENGINEERING VOLUME: 11 |NUMBER: 4 |2013 |SEPTEMBER from King Mongkut’s University of Technology North Bangkok (KMUTNB) in 2005 and 2011, respectively. He has been with department of Electrical Computer and Industrial technology, Faculty of Industrial Technology, Uttaradit Rajabhat University, Uttaradit, Uttaradit, Thailand since 2006. His research interests include electronic communications, analog signal processing and analog integrated circuit. c 2013 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 283