Demand for low-power low-voltage integrated circuits (ICs) has rapidly grown due to the increasing importance of portable equipment in all market segments including telecommunications, computers, and consumer electronics. The need for low-voltage ICs is also motivated by the new submicron CMOS technology scaling that requires all transistor gate-to-source (Vgs) voltage to operate in less than 1.5V in the year 2001 and 0.9V in 2009. as predicted by the Semiconductor Industry Association. In recent years, a lot of researches were done on designing switched-capacitor (SC) filters for low supply voltages. The primary reason is that SC filters achieve high filter accuracy with low distortion. SC filters that can operate with a single 1-V supply in standard CMOS process have been designed usi...[ Read more ]

Demand for low-power low-voltage integrated circuits (ICs) has rapidly grown due to the increasing importance of portable equipment in all market segments including telecommunications, computers, and consumer electronics. The need for low-voltage ICs is also motivated by the new submicron CMOS technology scaling that requires all transistor gate-to-source (Vgs) voltage to operate in less than 1.5V in the year 2001 and 0.9V in 2009. as predicted by the Semiconductor Industry Association. In recent years, a lot of researches were done on designing switched-capacitor (SC) filters for low supply voltages. The primary reason is that SC filters achieve high filter accuracy with low distortion. SC filters that can operate with a single 1-V supply in standard CMOS process have been designed using the switched-opamp technique without any clock voltage multiplier or low-threshold devices. However, this switched-opamp (SO) technique requires the opamps to turn off after their integrating phases and thus cannot be applied to realize a SC pseudo-N-path filter.

In this project, a modified switched-opamp technique has been proposed to realize a fully-differential 1-V SC pseudo-2-path filter in HP 0.5μm CMOS process with V_TP = 0.86V and V_Tn = 0.7V. A fully-differential two-output-pair switchable opamp is designed to achieve a low-frequency gain of 69dB to preserve the filter transfer function accuracy. With the use of SC dynamic level shifters, an output signal swing of 1.4-V_pp can be achieved even with a single 1-V supply. The filter implements a bandpass response with center frequency of 75kHz and bandwidth of 1.7kHz (Q=45) with a sampling frequency of 300kHz. It consumes a power of about 310μW and occupies a chip area of 800μmx l000μm.