HIGH PERFORMANCE CMOS REALIZATION OF THE THIRD GENERATION CURRENT CONVEYOR (CCIII)

1. HIGH PERFORMANCE CMOS REALIZATION OF THE THIRD GENERATION CURRENT CONVEYOR(CCIII) S. Minaei1, M. Yıldız1, H. Kuntman2, S. Türköz2 • Doğuş University, Department of Electronics and Communication Engineering, • 81010, Acıbadem, Kadıköy, Istanbul, TURKEY. 2. Istanbul Technical University, Faculty of Electrical and Electronics Engineering, Department of Electronics and Communication Engineering, 80626, Maslak, Istanbul .

2. ABSTRACT In this paper a new CMOS high performance dual-output realization of the third generation current conveyor (CCIII) is presented. The proposed CCIII provides good linearity, high output impedance at port Z and excellent input/output current gain. PSPICE simulation results using MIETEC 1.2 CMOS process model are included to verify the expected values.

3. 1. INTRODUCTION • Current conveyors and unity-gain amplifiers are widelyused by analog designers: • Signal processing • Active network synthesis • Recently third generation of this block has also been proposed by Fabre et al [3]. • The third generation current conveyors (CCIIIs) can be considered as a current controlled current source with a unity gain.

4. High performance current mirrors are required in the structure of the CCIII to provide: • Good dynamic swing • High output resistance which enables cascadability. • The main features of the CCIII are: • Low gain errors (high accuracy) • High linearity • Wide frequency response.

5. In this paper, we propose a novel implementation of dual-output CCIII based on an improved active-feedback cascode current mirrors (IAFCCM). • The proposed CCIII is compared with the conventional CCIII proposed in [3] and cascode CCIII. It provides: • High output resistance at port Z and • High dynamic swing.

6. 2. CIRCUIT DESCRIPTION • The port relations of an ideal dual-output CCIII is shown in Figure 1. Figure 1. Electrical symbol of the CCIII • The positive and negative signs define a positive and negative current-controlled conveyor.

7. The conventional third generation current conveyor is shown in Figure 2a [3]. • The conventional third generation current conveyor is shown in Figure 2 [3]. Figure 2b. Conventional (CCIII) core view from X and Y ports. Figure 2a. Conventional third generation current conveyor (CCIII).

8. A major advantage of this CCIII is its simple structure. • An important drawback of the conventional CCIII is the finite output resistance (Roz). • The Z+ output resistance of this current conveyor is, • Roz+ = (rds21)//(rds22) • where rdsi denotes the output resistance of the i’thtransistor respectively. • Third generation current conveyor using cascode current mirrors is shown in figure 3. • The cascode current mirrors between ports X-Y, X-Z+, and Y-Z- as shown in Figure 3. • Increase the accuracy of the current transformations in the CCIII.

9. Figure 3. Third generation current conveyor using cascode current mirrors. • The Z+ output resistance of the cascode CCIII is calculated as: • Roz+  (rds29 rds25 gm29)// (rds30rds26 gm30)

10. To increase the output resistance we propose a new CCIII based on using improved active-feedback cascode current mirror (IAFCCM) [10] in the output stages of the conveyor. • The proposed CCIII is shown in Figure 4. • The output resistance of the proposed CCIII is calculated as: • Roz+ = gm32 gm30 rds31 rds32 (rds30// rds28) //gm40 gm38 rds39 rds40 (rds38// rds34)

11. Figure 4. The proposed third generation current conveyor CCIII.

12. 3. SIMULATION RESULTS AND COMPARISON • The performance of the proposed CCIII shown in Figure 4, is verified by SPICE simulation program using, • MIETEC 1.2m CMOS process model parameters • PMOS transistor dimensions are W/L=720µm/2.4µm and, • NMOS transistor dimensions are W/L=240µm/2.4µm. • The voltage supply used for the proposed CCIII is 2.5V. • The main performances of the conventional, cascode and proposed CCIII are summarized in Table 1. • From Table 1 it can be seen that the performance of the proposed CCIII • is improved in terms of, • Linearity • gain accuracy • output resistance.

13. Figure 5. The relation between VX-VY for the proposed CCIII Figure 6. The relation between IX-IY-IZ for the proposed CCIII. Figure 8. The frequency response of the IZ+/IX and IZ-/IX Figure 7.The frequency response of the VX/VY

14. Table 1. Circuit performances.

15. 4. CONCLUSION • The proposed circuit uses improved active-feedback cascode current mirrors (IAFCCM), which increases output resistance at port-Z. • The proposed circuit is compared with the conventional and cascode CCIIIs. The simulation results confirm high performance of the circuits in terms of • Linearity • Voltage gain accuracy • Current gain accuracy..

16. 5. REFERENCES • Sedra A., Smith K.: ‘A Second-generation current conveyor and its applications’, IEEE Trans. On Circuit Theory, 1970, 17, pp.132-133. • Sedra A., Roberts G.: ‘The current conveyor: history, progress and new results’, IEE Proceeding Part G , 1990, 137, pp. 78-87. • Fabre A.: ‘Third generation current conveyor: a new helpful active element’, Electronics Letters, 1995, 31, pp.338-339. • Chow H.-C., Feng W.-S., ‘New symmetrical buffer design for VLSI application’, International Journal of Electronics., 2001, 88, pp.779-797. • Wang H.-Y., Lee C.-T.: ‘Systematic synthesis of R-L and C-D immittances using single CCIII’, International Journal of Electronics, (2000), 87, pp.293-301. • Horng J.-W., Weng R.-M., Lee M.-H., Chang C.-W.: ‘Universal active current filter using two multiple current output OTAs and one CCIII’, International Journal of Electronics., 2000, 87, pp. 241-247. • Mahmoud S.A., Soliman A.M., ‘Novel MOS-C oscillators using the current feedback op-amp’, International. Journal of Electronics, 2000, 87, pp. 269-280. • Abuelma’atti M. T., Alzaher H.A.: ‘Multi-function active-only current-mode filter with three inputs and one output’, International Journal of Electronics, 1998, 85, pp. 431-435. • Kuntman H., Çiçekoğlu O, Özoğuz S. ,: ‘A modified third generation current conveyor, its characteristic and applications’,Frequenz, 2002, 56, pp. 47-54. • Zeki A., Kuntman H.: ‘Accurate and high output impedance current mirror suitable for CMOS current output stages’, Electronics Letters, 1997,33, pp. 1042-1043.