Ladder-Type Gm -C Filters With Improved Linearity

A simple yet effective approach to improve the linearity of the transconductor-capacitor (G(m)-C) filters is proposed without any area or power overhead. Following a generalized nodal analysis, the transconductors of classical filter topology are rewired such that their input differential voltage lies within the linear regime. The effectiveness of the proposed method is validated through the design and simulation of a fifth-order Butterworth low-pass filter (LPF) in a standard 65-nm CMOS process. The proposed filter implementation occupies 0.0164 mm(2) (0.003 mm(2)/pole) die area and consumes 167-mu W for the cut-off frequency of 1-MHz. Operating at 1-V voltage supply, it shows an in-band total harmonic distortion (THD) of -49.14 dB for 200-mV peak-to-peak 1MHz differential voltage. An in-band 3rd-order intercept point (IIP3) of 9.36 dBm is also achieved with an in-band spurious-free-dynamic range (SFDR) greater than 53-dB, all of which reflect meaningful improvements relative to the classical architecture and despite the modest linearity performance of the internal G(m) stages.