10 MHz -3 dB Bandwidth 360 μw power source-follower low-pass filter for multi-channel acoustic analog front-end in CMOS 0.18 μm

This paper presents the complete design of a CMOS continuous-time analog filter that uses a single MOS transistor source-follower circuit to synthesize a 2nd-order low-pass transfer function. The filter is thought to operate in a multichannel (x64 pixels) analog front-end for ultrasound signal processing and hence has to consume limited power consumption (due to the elevate channel count) and perform relatively low-noise, while guaranteeing a certain Dynamic Range for the following A-to-D conversion stage. For these reasons this paper exploits a novel circuital biquadratic cell topology where the basic building block is the source-follower stage that has undoubting advantages of low power consumption and noise while maintaining large inband linearity. The design concept has been validated by extensive simulation results of a biquadratic cell prototype. The final filter prototype synthesizes a 4th-order transfer function and features 10 MHz -3 dB bandwidth. Power consumption is 360 μW from a single 1.8 V supply voltage, simulated Dynamic-Range at -40dBc of Total-Harmonic-Distortion is 61.3 dB. In-band IIP3 is 18.35 dBm for 34 MHz input tones.