Comparative Study of Resistorless Filters Using Differential Voltage Current Controlled Current Feedback Operational Amplifiers and Differential Voltage Current Controlled Current Conveyors
Differential Voltage Current Controlled Current Feedback Operational Amplifier is an attractive active element for realizing resistorless filters with a minimum active component count. This is verified through a design example, where a 3rd-order leapfrog filter has been realized using the AMS 0.35？μm CMOS process design kit. The performance of the Differential Voltage Current Controlled Current Feedback Operational Amplifier filter is evaluated and compared with that obtained by the corresponding filter, where Differential Voltage Current Controlled Current Conveyors have been employed. 1. Introduction The Current Feedback Operational Amplifier (CFOA) is a four terminal active element which offers particularly higher speed, higher slew rate, and better bandwidth than those achieved by the conventional voltage-mode op amps [1, 2]. A number of CFOA topologies with terminals of single type have been already introduced in the literature [3–6]. Enhanced CFOA topologies, including Fully Differential CFOAs (FDCFOAs) [7–10], Differential Voltage CFOAs (DVCFOAs) [11, 12], have been also published. Comparative studies of CFOAs and DVCFOAs have been performed in [4, 13], respectively. The realization of time-constants in filters, where the aforementioned types of CFOAs are utilized, is achieved by employing passive resistors. This is a drawback with respect to the nowadays analog filter realization trend, where resistorless filter structures with electronic tuning capability are preferred. As a solution, active resistors could be employed, but the performance of the resulted filter configurations in terms of linearity is worsened in this case. Resistorless topologies using CFOAs could be realized by employing the current controlled CFOA (CCCFOA) in [14]. The core of this active cell is constructed from translinear loops formed by a bipolar transistor. In addition, the minimum supply voltage requirement is equal to , where and are the base-emitter voltage of a bipolar transistor and saturation voltage of an MOS transistor, respectively. In order the CFOA filters to be compatible with the nowadays trend, a novel enhanced version of CFOA, mentioned as Differential Voltage Current Controlled Current Feedback Operational Amplifier (DVCCCFOA), will be employed for the realization of active filters. This cell has also the benefit for operating in a low-voltage power supply environment. As it will be proved through comparison results, the employment of the DVCCCFOA offers a reduced number of active component counts in comparison with the corresponding realizations, where
References
[1]
A. Payne and C. Toumazou, “Analog amplifiers: classification and generalization,” IEEE Transactions on Circuits and Systems I, vol. 43, no. 1, pp. 43–50, 1996.
[2]
A. M. Soliman, “Applications of the current feedback operational amplifiers,” Analog Integrated Circuits and Signal Processing, vol. 11, no. 3, pp. 265–302, 1996.
[3]
S. A. Mahmoud, H. O. Elwan, and A. M. Soliman, “Low voltage rail to rail CMOS current feedback operational amplifier and its applications for analog VLSI,” Analog Integrated Circuits and Signal Processing, vol. 25, no. 1, pp. 47–57, 2000.
[4]
G. Raikos and C. Psychalinos, “Low-Voltage current feedback operational amplifiers,” Circuits, Systems, and Signal Processing, vol. 28, no. 3, pp. 377–388, 2009.
[5]
B. J. Maundy, I. G. Finvers, and P. Aronhime, “Alternative realizations of CMOS current feedback amplifiers for low voltage applications,” Analog Integrated Circuits and Signal Processing, vol. 32, no. 2, pp. 157–168, 2002.
[6]
V. Kasemsuwan and W. Nakhlo, “Simple ± 0.75 volt rail-to-rail current feedback operational amplifier and its application for oscillator,” Frequenz, vol. 61, no. 11-12, pp. 249–253, 2007.
[7]
S. A. Mahmoud and I. A. Awad, “Fully differential CMOS current feedback operational amplifier,” Analog Integrated Circuits and Signal Processing, vol. 43, no. 1, pp. 61–69, 2005.
[8]
H. A. Alzaher, H. O. Elwan, and M. Ismail, “CMOS fully differential second-generation current conveyor,” Electronics Letters, vol. 36, no. 13, pp. 1095–1096, 2000.
[9]
A. H. Madian, S. A. Mahmoud, and A. M. Soliman, “Low voltage CMOS fully differential current feedback amplifier with controllable 3-dB bandwidth,” Analog Integrated Circuits and Signal Processing, vol. 52, no. 3, pp. 139–146, 2007.
[10]
A. A. El-Adawy, A. M. Soliman, and H. O. Elwan, “A novel fully differential current conveyor and applications for analog VLSI,” IEEE Transactions on Circuits and Systems II, vol. 47, no. 4, pp. 306–313, 2000.
[11]
E. O. Güne and A. Toker, “On the realization of oscillators using state equations,” AEU-Archiv fur Elektronik und Ubertragungstechnik, vol. 56, no. 5, pp. 317–326, 2002.
[12]
S. Gupta and R. Senani, “Grounded-capacitor SRCOs using a single differential difference complimentary current feedback amplifier,” IEE Proceedings: Circuits, Devices and Systems, vol. 152, no. 1, pp. 38–48, 2005.
[13]
P. Samiotis and C. Psychalinos, “Design of filters with only grounded passive elements using differential voltage current feedback operational amplifiers,” Journal of Circuits, Systems and Computers, vol. 19, no. 3, pp. 573–580, 2010.
[14]
M. Siripruchyanun, C. Chanapromma, P. Silapan, and W. Jaikla, “BiCMOS Current-Controlled Current Feedback Amplifier (CC-CFA) and its applications,” WSEAS Transactions on Electronics, vol. 5, no. 6, pp. 203–219, 2008.
[15]
C. Psychalinos and G. Souliotis, “Low-voltage current controlled current conveyor,” Analog Integrated Circuits and Signal Processing, vol. 63, no. 1, pp. 129–135, 2010.
[16]
H. Elwan and A. Soliman, “Novel CMOS differential voltage current conveyor and its applications,” IEE Proceedings: Circuits Devices and Systems, vol. 144, no. 3, pp. 856–860, 1997.
[17]
W. Chiu, S. I. Liu, and J. J. Chen, “CMOS differential difference current conveyors and their applications,” IEE Proceedings: Circuits Devices and Systems, vol. 143, no. 2, pp. 91–96, 1996.
