Design of Continuous-Time OTA-C Elliptic Filter for CMOS VLSI

CMOS VLSI를 위한 연속시간의 OTA-C Elliptic 필터 설계

Design of a continuous-time fifth-order OTA-C Eiliptic filter for operation at 4MHz is presented. The filter has been realize by five OTAs, eight capacitors and a buffer as an OTA-C structure. To prevent decreasing of characteristics due to the parastic capacitance of OTA and loading a buffer and a capacitor have been connected to the next of second section. As the result the frequency characteristics were found to be essentially within specifications : less than 0.2dB passband attenuation, 30dB stopband attenuation and 4Mz cut-off frequency have been obtained and the characteristic of cut-off region has been improved about 7dB compared with it of the theoretical case.

본 논문에서는 차단주파수가 4MHz인 연속시간의 5차 OTA-C Elliptic filter를 설계하였다. 설계된 필터는 OTA-C구조로서 5개의 OTA, 8개의 커패시터와 1개의 완충기로 구성하였다. OTA의 기생커패시턴스 및 Loading에 의한 특성저하를 방지하기 위해 완충기와 커패시터를 설계하여 연결시켰고, 이로인해 주파수특성은 원래의 설계조건, 즉 통과대역 감쇠 0.2dB이하, 저지대역 감쇠 30dB와 차단주파수 4MHz를 모두 만족시켰으며, 차단특성은 이론적인 경우보다 약 7dB만큼 더욱 특성이 개선되었다.