Low-power MOSFET-C 120 MHz Bessel allpass filter with extendedtuning range

摘要

An integrated delay cell for a disc-drive read channel has toncombine a high 120 MHz bandwidth with a low power dissipation and anlarge 1:6 tuning range. Because of linearity and transfer requirements,nthe implementation is a continuous-time third-order Bessel allpassnfilter. An opamp-MOSFET-C configuration is best for low powernconsumption but has two problems: a small tuning range and often a lownbandwidth. The author gives solutions to both problems, including anpatented tuning-range extension circuit. Measurements show that thendesign method works well. The cell dissipates 15 mW at 27°C