An Enhanced Adaptive $Q$-Tuning Scheme for a 100-Mhz Fully Symmetric OTA-Based Bandpass Filter Academic Article uri icon


  • A tuning scheme for continuous-time high- Q biquad filters is presented. An improvement over the existing implementation of the modified-LMS Q-tuning scheme is proposed and efficiently combined with the frequency tuning based on phase-locked loops. The proposed scheme takes much less area without compromising the accuracy achieved previously. The proposed unified Q-and fo-tuning scheme does not require the Q-tuning loop to be slower than the fo-tuning loop. The optimal case is to have equal speeds for both loops. Also, a low-voltage pseudo-differential operational transconductance amplifier with inherent common-mode feedforward is introduced. The structure is fully symmetric and suitable for high-frequency applications. An experimental test chip is fabricated in standard CMOS 0.5-μ technology, with a bandpass filter of center frequency 100 MHz and Q of 20, along with the proposed tuning scheme. The measured Q-tuning error is around 1%. Expected and experimental results are in good agreement.

altmetric score

  • 3

author list (cited authors)

  • Kallam, P., Sánchez-Sinencio, E., & Karşılayan, A.

citation count

  • 40

publication date

  • April 2003