Design of tunable differential transconductance-capacitance low pass filter

Abstract

This project presents the design of a tunable differential transconductancecapacitance (gm-C) low pass filter for hearing aid application. Low power consumption and transconductor with very low transconductance are the main focus and challenges in this project. Several low transconductance OTA and low power design techniques published are discussed and compared. A differential 3rd order gm- C low pass filter is designed and characterized at typical process corners and compared with cross skew corners down to layout level design base on TSMC 0.25µm process technology. The active silicon area is estimated to be ~8mm2 working at 1.35V with a typical hearing aid 1.4V Zinc-air battery. The filter designed dissipates ~12µW and the -3 dB cut-off frequency is 10.5 KHz with -20 dB attenuation at around 22 KHz. Simulation results are shown and are in good agreement with the theoretical results. Tanner Tools S-edit and L-edit are used in this project for schematics and layout design and simulated using Tanner T-Spice simulator.