Design of a Tunable 4th Order OTA-C Band-Pass Filter for Use in Front-End of ADC

This article presents a tunable fourth-order band-pass filter that is designed using an operational trans-conductance amplifier (OTA), which can be used as an anti-aliasing filter (AAF) in the front-end of an analog-to-digital converter (ADC). It is necessary to use a suitable filter to prevent unwanted signals from entering the ADC. The bandwidth of the AAF should be designed according to the bandwidth of the ADC, therefore, matching these two bandwidths is one of the important challenges when using multi-bandwidth analog to digital converters in digital communication applications. The proposed band-pass filter is designed and simulated in 180 nm CMOS technology. The simulation results show that by changing the two bias voltages of the proposed filter, its bandwidth can be changed according to the frequency range of ADSL, ADSL2, and ADSL2+ communication standards and it effectively attenuates unwanted signals.