Abstract

In this paper, a low-voltage low-power CMOS operational amplifier using the composite cascode technique is presented. This technique has been employed in the differential input pair and output transistors to enhance the gain of op-amp. Also, indirect compensation is used to improve the frequency response of the op-amp and avoids instability when a large capacitive load at the output of the op-amp must be handled. Two-stage op-amp is designed and simulated in a TSMC 0.18 μm CMOS technology, to evaluate the proposed technique. The sub-threshold region is employed in the design to use the low supply voltage and reduce power consumption effectively. The op-amp operates at a 0.7 V power supply with 891 nW power consumption. The open-loop gain is 90.1 dB, the unity gain-bandwidth (UGBW) is 309 kHz, and the phase margin is 57.6 degree under 15 pF load.

References

• M. E. Schlarmann, S. Q. Malik, and R. L. Geiger, “Positive Feedback Gain-Enhancement Techniques for Amplifiers Design,”  IEEE International Symposiums on Circuits and Systems, Vol. 2,  pp. 37-40, 2002.
• SU Li, and Qiu Yulin, “Design of a Fully Differential Gain-boosted Folded-Cascode Op Amp with Settling Performance Optimization,” IEEE Conference on Electron Devices and Solid-State Circuits, pp. 441-444, 2005.
• S. A. Zabihian, and R. Lotfi, “A Sub-1-V High Gain Single Stage Operational Amplifier,” IEICE Electronics Express, Vol. 5, No.7, pp. 211-216, 2008.
• D. J. Comer, D. T. Comer, and R. P. Singh, “A High-gain, Low-power CMOS Op Amp using Composite Cascode Stages,” in Proceedings of the 53rd IEEE International Midwest Symposium on Circuits and Systems, 600–603, 2010.
• R. P. Singh, D. J. Comer, T. Waddel, D. T. Comer, and K.  Layton,  “High-gain microwatt composite cascode op amps,” International Journal of Electronics, Vol. 99, No. 9, pp. 1179-1190, 2012.
• D. T. Comer, D. J. Comer, and L. Li, “A high-gain complementary metal-oxide semiconductor op amp using composite cascode stages,” International Journal of Electronics, Vol. 97, No. 6, pp. 637-646, 2010.
• A. Esmaili, H. Babazadeh, Kh. Hadidi, and A. Khoei, “Bulk Driven Indirect Feedback Compensation Technique for Low-Voltage Applications,” 21st Iranian Conference on Electrical Engineering, pp. 1-5, 2013.
• V. Saxena, and R. Baker, “Indirect feedback compensation of CMOS op-amps,” IEEE Workshop on Microelectronics and Electron Devices, pp. 3-4, 2006.
• V. Saxena and R. Baker, “Indirect compensation techniques for three-stage CMOS op-amps,” 52nd IEEE International Midwest Symposium on Circuits and Systems, pp. 9-12, 2009.
• V. Saxen,a and R. Baker, “Indirect compensation techniques for three-stage fully-differential op-amps,” 53rd IEEE International Midwest Symposium on Circuits and Systems, pp. 588-591, 2010.
• V. Saxena, and R. Baker, “Indirect Compensation Technique for Low-Voltage Op-Amps,” in Proceedings of the 3rd Annual Austin Conference on Integrated Systems and Circuits, pp. 1-4, 2008.
• K. Ahuja, “An improved frequency compensation technique for CMOS operational amplifiers”, IEEE Journal of Solid-State Circuits, Vol. SC-18, No. 6, pp.629-633, 1983.
• G. Palmisano, and G. Palumbo, “A Compensation Strategy for Two-Stage CMOS OPAMS Based on Current Buffer,” IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, Vol. 44, No. 3, pp. 252–262, 1997.
• Gh. Moradi, M. R. Alamdar, and S. Izadpanah Toos, “Hybrid Frequency Compensation to Improve Unity-Gain Bandwidth of Low-Voltage Low-Power CMOS Operational Amplifiers,” Majlesi Journal of Telecommunication Devices, Vol. 7, No. 2, pp. 65–72, 2018.
• L. Li, “High Gain Low Power Operational Amplifier Design and Compensation Techniques,” Ph.D. Thesis, Brigham Young University, 2007.
• A. Soltani, M. Yaghmaie, B. Razeghi,R. Pourandoost, S. Izadpanah Tous, and Abbas Golmakani, “Three stage low noise operational amplifier design for a 0.18 um CMOS process,” 9th International Conference on Electrical Engineering, Computing Science and automatic Control (CCE), 2012 .
• Samuel Martin, Vance D. Archer III, David M. Boulin, Michel R. Frei, Kwok K. Ng, and Ran-Hong Yan , “Device Noise in Silicon RF Technologies,” Bell Labs Technical Journal, Summer 1997.
• E. Kargaran, M. Sawan, Kh. Mafinezhad, H. Nabovati, “Design of 0.4V, 386nW OTA Using DTMOS Technique for Biomedical Applications,” 55th IEEE International Midwest Symposium on Circuits and Systems, pp. 270–273, 2012.
• M. R. Valero, S. Celma, N. Medrano, B. Calvo, and C. Azcona, “An Ultra Low-Power Low-Voltage Class AB CMOS Fully Differential OpAmp,” IEEE International Symposium on Circuits and Systems, pp. 1967-1970, 2012.
• A. Tanaka, Z. Qin, H. Yoshizawa, “A 0.5-V 85-nW rail-to-rail operational amplifier with a cross-coupled output stage,”  IEEE 20th International Conference on Electronics, Circuits, and Systems (ICECS), pp. 137-140, 2013.
• M. R. Valero Bernal, S. Celma, N. Medrano and B. Calvo, “An ultralow-power low-voltage class-AB fully differential OpAmp for long-life autonomous portable equipment,”  IEEE Transactions on Circuits and Systems II: Express Briefs, Vol. 59 , No. 10 , pp. 643-647, 2012.
• M. Razzaghpour, and A. Golmakani, “An ultra-low-voltage ultra-low power OTA with improved gain-bandwidth product,” International Conference on microelectronics, pp. 39-42, 2008.
• S. A. Zabihian, and R. Lotfi, “Ultra-low-voltage, low-power, high-speed operational amplifiers using body-driven gain-boosting technique,” IEEE International Symposium on Circuits and System, pp. 705- 708, 2007.
• Table 2. The Size of transistors, Capacitors, and Reference Current
• 
• 
• proposed
• 
• 
• 
• 
• 
• Technology (µm)
• 0.18
• 0.18
• 0.18
• 0.18
• 0.18
• 
• Power supply (mV)
• 700
• 500
• 800
• 500
• 700
• 
• Power consumption (µW)
• 0.891
• 0.085
• 1.2
• 1.02
• 82
• 
• Gain (dB)
• 90.1
• 101
• 51
• 88.5
• 74.2
• 
• Phase margin (Degree)
• 57.6
• 50.59
• 60
• 66.3
• 76.5
• 
• Unity gain-bandwidth (kHz)
• 309
• 8.6
• 57
• 83.88
• 25000
• 
• CMRR (dB)
• 100.3@ 10 Hz
• 90 @ DC
• -----
• 133.85
• -----
• 
• PSRR (dB)
• 120.6 @ 10 Hz
• -----
• -----
• -----
• -----
• 
• Slew Rate (V/µs)
• 0.065
• -----
• 0.14
• 0.052
• 13
• 
• Input referred noise (