This paper proposes a study of input impedance of 2 types of CMOS active inductors. It derives 2 input impedance formulas. The first formula is the input impedance of the grounded active inductor. The second formula is the input impedance of the floating active inductor. After that, these formulas can be used to simulate magnitude and phase response of input impedance as a function of current consumption with MATLAB. Common mode rejection ratio (CMRR) of the fully differential bandpass amplifier is derived based on superposition principle. CMRR as a function of input frequency is plotted as a function of current consumption. <\/p>\r\n","references":"[1]\tA. Thanachayanont, A. Payne, \"VHF CMOS integrated active inductor\u201d, Electronic Letters, 23rd May 1996, Vol.32, No.11 pp.999-1000.\r\n[2]\tU. Yodprasit, J. Ngarmnil, \"Q- enhancing technique for RF CMOS active inductor\u201d, ISCAS2000, pp V-589-V-592\r\n[3]\tChao-Chih Hsiao, Chin-Wei Kuo, Chien-Chih Ho, Yi-Jen Chan, \" Improved Quality factor of 0.18 um CMOS active inductor by a feedback resistance design\u201d, IEEE Microwave and Wireless Components letters, Vol.12, No.12, December 2002, pp.467-469\r\n[4]\tY.-J. Jeong, Y.-M. Kim, H.-J. Chang, T.-Y. Yun, \"Low power CMOS VCO with a low-current, high Q active inductor\u201d, IET Microw. Antennas Propag, 2012, Vol.6, Iss. 7, pp.788-792\r\n[5]\tA. Thanachayanont, A. Payne, \" CMOS floating active inductor and its applications to bandpass filter and oscillator designs\u201d, IEE Proc.-Circuits Devices Syst., Vol.147, No.1, February 2000, pp.42-48\r\n[6]\tLiang-Hung Lu, Hsieh-Hung Hsieh, Yu-Te Liao, \" A Wide Tuning Range CMOS VCO with a differential tunable active inductor\u201d, IEEE Transactions on Microwave Theory and Techniques, Vol.54, No.9, September 2006, pp. 3462-3468\r\n[7]\tPaul R. Gray, Paul J. Hurst, Stephen H. Lewis, Robert G. Meyer, \"Analysis and Design of Analog Integrated Circuits\u201d, 4th edition, Copyright 2001, John Wiley & Sons, pp.221-224\r\n[8]\tAdel S. Sedra, Kenneth C. Smith, \" Microelectronic Circuits\u201d, 5th edition, Copyright 2004, Oxford University Press, 2004, pp.355\r\n","publisher":"World Academy of Science, Engineering and Technology","index":"Open Science Index 84, 2013"}