Voltage Mode Quadrature Oscillator Employing Single Differential Voltage Current Controlled Conveyor Transconductance Amplifier

Transcription

1 nternational Journal o Electronics and Electrical Engineering Vol. 3, No. 5, October 25 Voltage Mode Quadrature Oscillator Employing Single Dierential Voltage Current Controlled Conveyor Transconductance Ampliier S. Maiti and R. R. Pal Department o Physics and Technophysics, Vidyasagar University, Midnapore 722, West Bengal, ndia saikat_physics@yahoo.com, rrpal@mail.vidyasagar.ac.in current conveyor (DDCC) [], [], dierential voltage current conveyor (DVCC) [2]-[4], current dierencing transconductance ampliier (CDTA) [5], [6] and recently by the current controlled current conveyor transconductance ampliier (CCCCTA) [7], [8] have received considerable attention. But a careul study o these reported works reveals that several circuits suer rom one or more o the ollowing drawbacks: (i) The oscillators reported in [3]-[6], [9], [], [3] use two or more active blocks and at least ive passive components. (ii) The oscillators proposed in [6] do not provide inherent control to the requency o oscillation and the condition o oscillation. (iii) The oscillator realizations in [3]-[4] do not provide any electronic control o either the requency o oscillation or the condition o oscillation. (iv) Moreover, the oscillator realizations in [], [2], [4], [5], [7] can not provide quadrature voltage or current outputs directly. (v) The circuits proposed in [5], [], [5] employ loating capacitors which are not suitable or monolithic circuit implementation. (vi) Also in the circuit proposed in [2] one o the DVCC has one o its input Y terminal grounded while in the circuit proposed in [] one o the DDCC has two o its input Y terminal grounded. n 29, a new active element called the dierential voltage current conveyor transconductance ampliier (DVCCTA) has been proposed [9]. Several voltage mode and current mode quadrature oscillator using DVCCTA and DVCCCTA have been proposed [2]-[22]. The oscillator proposed in [22] consists o two irst order voltage mode all pass ilters in cascade. Also the second DVCCTA has one o its input Y terminal (Y2) grounded. The motivation o this paper is to present a low voltage second order voltage mode quadrature oscillator using the dierential voltage current controlled conveyor transconductance ampliier. The circuit employs single dierential voltage current controlled conveyor transconductance ampliier, two grounded capacitors and two grounded resistors. The proposed quadrature oscillator circuit provides the ollowing advantages: First, the condition o oscillation and the requency o Abstract This paper presents a second order voltage mode quadrature sinusoidal oscillator using a recently reported active building block, namely the dierential voltage current controlled conveyor transconductance ampliier. The circuit proposed here employs single dierential voltage current controlled conveyor transconductance ampliier, two grounded resistors and two grounded capacitors. The use o grounded capacitors makes the circuit suitable or monolithic circuit implementation. The proposed circuit enjoys the advantage o the independent control o the condition o oscillation and the requency o oscillation. Also the condition o oscillation and the requency o oscillation can be tuned electronically by the use o separate bias currents. The non ideal analysis and the sensitivity analysis o the proposed oscillator circuit have been carried out. This shows that the circuit exhibits low active and passive sensitivities. PSpice simulation results have been included which veriy the workability o the proposed circuit. ndex Terms quadrature oscillator (QO), dierential voltage current controlled conveyor transconductance ampliier (DVCCCTA), voltage mode, condition o oscillation (CO), requency o oscillation (FO). NTRODUCTON The sinusoidal oscillators have become very important building elements or analog systems and are requently used in electrical and electronics engineering works. Among them the quadrature sinusoidal oscillators have become very important circuit or various communication applications wherein there is a requirement o multiple sinusoids which are 9ºphase shited and are requently used in telecommunications or quadrature mixers, or measurement purposes in vector generators or selective voltmeters and in single sideband modulations [], [2]. At the present time designing electronic circuits which can operate rom low voltages has been gaining increasing interests because the battery operated portable devices require low power dissipation to increase battery lie. Several realizations o sinusoidal oscillators based on various active building blocks (ABBs) like second generation current conveyor (CC) [3], [4], current eedback ampliier (CFA) [5], current dierencing buered ampliier (CDBA) [6]-[9], dierential dierence Manuscript received January, 24; revised October 2, Engineering and Technology Publishing doi:.272/ijeee

2 nternational Journal o Electronics and Electrical Engineering Vol. 3, No. 5, October 25 oscillation are independently adjustable by the use o separate bias currents. The second reason is that the use o grounded capacitors makes the circuit suitable or monolithic implementation because the grounded capacitors can compensate or the stray capacitances at their nodes [23]. The third reason arises due to the transconductance stage because the transconductance ampliier provides the eature o electronic tuning to the circuit parameters. The circuit also oers low active and passive sensitivities.. where Rx represents the inite parasitic resistance at the X input terminal, gm and gm2 represent the transconductance gains o the irst and second OTAs. DFFERENTAL VOLTAGE CURRENT CONTROLLED CONVEYOR TRANSCONDUCTANCE AMPLFER Figure. The schematic symbol o the DVCCCTA. The dierential voltage current controlled conveyor transconductance ampliier [2] is an active building block which consists o two principal building blocks, a dierential voltage current controlled conveyor at the ront end and operational transconductance ampliiers at the rear end. The DVCCCTA has all the advantages o both dierential voltage current controlled conveyor and operational transconductance ampliiers. The circuit symbol and the equivalent circuit o the DVCCCTA are shown in Fig. and Fig. 2 respectively, where Y and Y2 are the input terminals and Z, O+ and O2+ are the output terminals. The DVCCCTA is characterized by the ollowing equations Y Y 2 V R X x Z O O 2 X VY VY 2 g m VZ g m 2 Figure 2. Equivalent circuit o the DVCCCTA. A possible bipolar implementation o the proposed DVCCCTA is shown in Fig. 3. For this case the values o the parameters can be expressed as Rx () VT, g m B 2, g m 2 B3 2 B 2VT 2VT (2) where B, B2 and B3 are the bias currents and VT is the thermal voltage whose value is 26mV at 27ºC. For large value o B the eect o Rx could be neglected. Figure 3. A possible bipolar implementation o the DVCCCTA.. The proposed quadrature oscillator circuit employing single DVCCCTA is shown in Fig. 4. The circuit employs two grounded capacitors and two grounded resistors. The proposed quadrature oscillator circuit is derived rom [2]. Using () and doing routine circuit analysis, the characteristic equation can be written as PROPOSED QUADRATURE OSCLLATOR CRCUT s 2CC2 RR2 sc R R2 RR2 g m2 g mr2 (3) t is seen rom (3) that the condition o oscillation (CO) and the requency o oscillation (FO) can be expressed as CO : g m2 Figure 4. Proposed quadrature oscillator circuit using DVCCCTA. 25 Engineering and Technology Publishing 345 R2 R (4)

3 nternational Journal o Electronics and Electrical Engineering Vol. 3, No. 5, October 25 FO : osc 2 g m CC 2 R Taking into account the ollowing non idealities the modiied expression o the condition o oscillation (CO) and the requency o oscillation (FO) can be expressed as (5) Thereore the condition o oscillation can be adjusted by gm2 and the requency o oscillation can be adjusted by gm i.e., they are independently adjustable by the separate bias currents B3 and B2, respectively. The two marked quadrature voltages in Fig. 4 are related as Vout2 jkvout where k o C g m CO : gm2 FO : osc (6) 2 S osc S osc S osc S g osc m 2 (9) () CO 2 C CO (2) C2 (3) CZ (4) CO 2 (5) R 2 R Rx (6) Rx 2 R Rx (7) O The non ideal DVCCCTA can be characterized by the ollowing equations [2] 2 Z O 2 () C 2 C CO (7) S Rosc S Rosc where α and α2 represent the voltage transer gains rom Y and Y2 terminal to the X terminal, β represents the current transer gain rom X to Z terminal and γ and γ2 are the current transer gains rom Z terminal to O+ and O2+ terminals, respectively. They depend on the requency o operation, transistor parameters and temperature. n practical, α= ε, α2= ε2, β= ε3, γ= ε4 and γ2= ε5. The parameters ε and ε2 ( ε, ε2 «) are the voltage tracking errors o the voltage inverting stages and ε3, ε4 and ε5 ( ε3, ε4, ε5 «) denote the current tracking errors o the current inverting stages o the DVCCCTA. These gains are ideally equal to unity. The input parasitic resistance Rx appears in series with the external resistor R. Thereore this parasitic resistance increases the external resistor R as R=R+Rx. The parasitic resistances RZ, RO+, RO2+ and parasitic capacitance CZ, CO+ and CO2+ appear between the high output impedance terminals Z, O+, O2+ and ground. Since the values o RZ and RO2+ are in the order o MΩ, thereore an external resistor R2 should be connected at this terminal so that RZ RO2+ R2 R2. The parasitic capacitances CO+ and (CZ +CO2+) are absorbed into the external capacitors C and C2, respectively, as they appear in shunt with them. Thereore the original capacitances C and C2 are increased to C and C2, where C=C+CO+ and C2=C2+CZ +CO Engineering and Technology Publishing (8) The active and passive sensitivities o the oscillation requency are given as X V Y VY 2 g m VZ 2 g m R Rx C CO C2 CZ CO 2 R Rx NON DEAL ANALYSS AND SENSTVTY ANALYSS Y Y2 V R 2 X x Z O O 2 g m t is evident that the quadrature outputs would have equal magnitude or k=. t is clear rom (6) that k depends on the oscillation requency i.e. on the transconductance gain gm and thereore it is temperature dependent term. Thus the changing o the oscillation requency by gm simultaneously changes the ratio o the magnitudes o quadrature voltages. Also the circuit provides output voltages rom high impedance port. Thereore or explicit utilization voltage buers would be required. V. 2 R2 x Thereore the circuit exhibits low active and passive sensitivities. V. SMULATON RESULTS To veriy the theoretical prediction, the proposed quadrature oscillator circuit has been simulated using PSpice simulation program using the bipolar implementation o the DVCCCTA as shown in Fig. 3. The supply voltages were chosen as VCC= VEE=.5V. The quadrature oscillator was designed by using the ollowing set o passive elements: C=68pF, C2=68pF, R=2kΩ and R2=kΩ. The bias currents were chosen as B=5µA (Rx=26Ω), B2=5µA (gm=.96ms) and B3=25µA (gm2=.48ms). With these values, the condition o oscillation is satisied. The simulated startup o oscillations or both the quadrature voltages Vout and Vout2 is shown in Fig. 5. The steady state is reached approximately within 3μs. The simulated output waveorms in steady state are shown in Fig. 6. This yields the oscillation requency o khz. Fig. 7 shows the simulated requency spectrums o V out and Vout2. The total harmonic distortions (THD) at both the outputs are less than %. The total power consumption is approximately.46mw. 346

4 nternational Journal o Electronics and Electrical Engineering Vol. 3, No. 5, October 25 ACKNOWLEDGMENT This work was supported in part by a grant rom Special Assistance Programme-University Grants Commission, ndia. The authors also grateully acknowledge the inancial support rom FST, Department o Science and Technology, ndia to carry out the research work. REFERENCES [] Figure 5. The Simulated output waveorms o the proposed quadrature oscillator at transient stage. [2] [3] [4] [5] [6] Figure 6. The steady state waveorms o the quadrature voltages. [7] [8] [9] [] Figure 7. The simulated FFT spectrum o the quadrature voltages. V. [] CONCLUSON [2] n this paper, a new quadrature oscillator topology working in the voltage mode has been presented. The proposed circuit employs single dierential voltage current controlled conveyor transconductance ampliier, two grounded capacitors and two grounded resistors. The use o grounded capacitors makes the circuit suitable or monolithic implementation. The oscillator circuit proposed in this paper provides non-interactive control o the condition o oscillation and the requency o oscillation. Also the condition o oscillation and the requency o oscillation can be tuned electronically by the separate bias currents. The non ideal analysis and the sensitivity analysis o the oscillator circuit have been provided. The magnitudes o the active and passive sensitivities are not more than unity. PSpice simulation results have been included that conirmed the workability o the proposed quadrature oscillator circuit. 25 Engineering and Technology Publishing [3] [4] [5] [6] [7] 347. A. Khan and S. Khwaja, An integrable gm-c quadrature oscillator, nternational Journal o Electronics, vol. 87, no., pp , 2. M. T. Ahmed,. A. Khan, and N. Minhaj, On transconductance C quadrature oscillators, nternational Journal o Electronics, vol. 83, no. 2, pp. 2-27, 997. N. Minhaj, Current conveyor-based voltage mode two-phase and our phase quadrature oscillators, nternational Journal o Electronics, vol. 94, no. 7, pp , 27. N. Minhaj, Dual-Output second-generation current conveyorbased voltage-mode sinusoidal oscillator modiied or chaos generators, nternational Journal o Recent Trends in Engineering, vol. 2, no. 5, pp , 29. W. Tangsrirat and W. Surakampontorn, Single-ResistanceControlled quadrature oscillator and universal biquad ilter using CFOAs, AEU-nternational Journal o Electronics and Communication, vol. 63, no. 2, pp. 8-86, 29. W. Tangsrirat, D. Prasertsom, T. Piyatat, and W. Surakampontorn, Single-Resistance-Controlled quadrature oscillators using current dierencing buered ampliiers, nternational Journal o Electronics, vol. 95, no., pp. 9-26, 28. W. Tangsrirat, Novel minimum-component universal ilter and quadrature oscillator with electronic tuning property based on CCCDBAs, ndian Journal o Pure and Applied Physics, vol. 47, pp , 29. S. Pisitchalermpong, D. Prasertsom, T. Piyata, W. Tangsrirat, and W. Surakampontorn, Current tunable quadrature oscillator using only CCCDBAs and grounded capacitors, in Proc. The Fourth nternational Conerence on Electrical Engineering/Electronics, Computer, Telecommunications and normation Technology (ECT-CON 7), 27, pp W. Tangsrirat, T. Pukkalanun, and W. Surakampontorn, CDBABased universal biquad ilter and quadrature oscillator, Active and Passive Electronic Components, vol. 28, 28. M. Kumngern and K. Dejhan, DDCC-Based quadrature oscillator with grounded capacitors and resistors, Active and Passive Electronic Components, vol. 29, 29. S. Kilinc, V. Jain, V. Aggarwal, and U. Cam, Catalogue o variable requency and single-resistance-controlled oscillators employing a single dierential dierence complementary current conveyor, Frequenz, vol. 6, pp , 26. P. Kumar, A. U. Keskin, and K. Pal, DVCC-Based single element controlled oscillators using all-grounded components and simultaneous current-voltage mode outputs, Frequenz, vol. 6, pp. 4-44, 27.. A. Khan and P. Beg, Fully dierential sinusoidal quadrature oscillator using CMOS DVCC, in Proc. nternational Conerence on Communication, Computer and Power (CCCP 9), Muscat, 29, pp V. Aggarwal, S. Kilinc, and U. Cam, Minimum component SRCO and VFO using a single DVCCC, Analog ntegrated Circuits and Signal Processing, vol. 49, pp. 8-85, 26. D. Prasad, D. R. Bhaskar, and A. K. Singh, Realization o singleresistance-controlled sinusoidal oscillator: A new application o the CDTA, WSEAS Transactions on Electronics, vol. 5, no. 6, pp , 28. W. Jaikla, M. Siripruchyanun, J. Bajer, and D. Biolek, A simple current-mode quadrature oscillator using single CDTA, Radioengineering, vol. 7, no. 4, pp. 33-4, 28. M. Siripruchyanun and W. Jaikla, Current controlled current conveyor transconductance ampliier (CCCCTA): A building block or analog signal processing, Electrical Engineering, vol. 9, no. 6, pp , 28.

5 nternational Journal o Electronics and Electrical Engineering Vol. 3, No. 5, October 25 [8] S. Maiti and R. R. Pal, Dual mode quadrature oscillator employing single current controlled current conveyor transconductance ampliier, nternational Journal o nnovative Research in Science, Engineering and Technology, vol. 2, no. 7, pp , 23. [9] A. Jantakun, N. Pisutthipong, and M. Siripruchyanun, A synthesis o temperature insensitive/electronically controllable loating simulators based on DV-CCTAs, in Proc. The Sixth nternational Conerence on Electrical Engineering/Electronics, Computer, Telecommunications and normation Technology (ECT-CON 29), Pattaya, Thailand, 29, pp [2] A. Lahiri, W. Jaikla, and M. Siripruchyanun, Voltage-Mode quadrature sinusoidal oscillator with current tunable properties, Analog ntegr. Circ. Sig. Process., vol. 65, pp , 2. [2] W. Jaikla, M. Siripruchyanun, and A. Lahiri, Resistorless dualmode quadrature sinusoidal oscillator using a single active building block, Microelectronics Journal, vol. 42, pp. 35-4, 2. [22] N. Pandey, R. Pandey, and S. K. Paul, A irst order all pass ilter and its application in a quadrature oscillator, Journal o Electron Devices, vol. 2, pp , 22. [23] A. M. Soliman, New grounded capacitor current mode band-pass low-pass ilters using two balanced output CC, Journal o Active and Passive Electronic Devices, vol. 3, pp , 28. Radha R. Pal was born in 967 in West Bengal, ndia. He passed his B.Sc. and M.Sc. degrees in Physics rom Burdwan University, ndia in the years 986 and 988 respectively and topped the list in both the examinations. He got his Ph.D. degree rom ndian nstitute o Technology, Kharagpur, ndia in the year 996. His Ph.D. topic was Studies on Voltage/Current controlled oscillators using Complementary Bipolar nverter Cells. He joined Bengal Engineering College (Deemed University) (now Bengal Engineering and Science University) as a Lecturer in Physics in the year 995. Presently he is working as a Proessor in Physics in the Vidyasagar University, Midnapore, ndia. His research interest is Low voltage/low power integrated circuit design, VCO and PLL design and simulation. The designs are based on both CMOS and bipolar devices. Some other topics o interest are MEMS pressure sensor design, design o the interacing circuits o MEMS based on low voltage/low power topology, generation o shock waves under water, etc. Saikat Maiti was born in 984 in West Bengal, ndia. He received his B.Sc. and M.Sc. degrees in Physics rom Vidyasagar University, Midnapore, West Bengal, ndia in 25 and 27 respectively. He is currently pursuing the Ph.D. degree at the Department o Physics and Technophysics, Vidyasagar University. His research interests include low voltage and low power analog circuit design, analog signal processing and mixed mode circuit design. 25 Engineering and Technology Publishing 348