• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.4
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• pp.293-299
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• 2004

An active RC 2nd order Butterworth filter suitable for a baseband channel-selection filter of a direct conversion receiver is presented. The linearity of the 2nd order Butterworth filter is analyzed. In order to improve the linearity of the filter, the operational amplifiers should have a high linear gain and low 3rd harmonic, and the filter should be designed to have large feedback factor. This second order Butterworth filter achieves-14dBV in-channel (400kHz, 500kHz) IIP3, +29dBV out-channel (10MHz, 20.2MHz) IIP3 and 15.6 $nV/\sqrt{Hz}$ input-referred noise and dissipates 10.8mW from a 2.7-V supply. The analysis and experimental results are in good agreement