In this paper, the relationship between the bandwidth (BW) and power efficiency of a source follower based (SFB) filter is quantitatively analyzed, and a design methodology for a SFB filter for optimized BW - power consumption is introduced. The proposed design methodology achieves a maximum BW at a target quality (Q) factor for the given power consumption constraint by controlling design factors individually. In order to achieve the target BW from the maximized BW, a tuning method is introduced. Through the proposed design methodology, a fourth order Butterworth filter was implemented in 0.18 ${mu}m$ CMOS technology. The measured BW, power consumption, and IIP3 are 100 MHz, 33 ${mu}W$, and 9 dBm, respectively. Compared with other filter structures, the measured results show high BW - power efficiency.