Research And Realization Of The Current Mode Log-Domain Filters

The important features of the current development of active filters are highintegration, component unicity and full MOS. Although the research of filters hasmade great progress and has obtained brilliant achievements, the full integration ofcontinuous time filters still faces many problems and difficulties to be overcome inthe realization. The main problems lie in the following aspects: the stability offrequent response, high frequency properties, dynamic range and noise problem,power consumption and dynamic range etc. Low-power and low-voltage analogcircuit design is one of the resaerch focuses that attract many researchers. The companding is one of the technologies which aims to low voltage, lowpower and large dynamic range design. The realization and performance analysis oflog-domain filter is the main topic of this dissertation. In this dissertation, the realization of single end and differential log-domainfilters is discussed. The amplitude-frequency characteristics, noise performance anddistortion performance of log-domain integrators and high order log-domain filtersare analyzed. Output noise and dynamic range expressions of the log-domain filtersare deduced. The technology of dynamic biasing log-domain filter, which can reducethe system noise, increase the dynamic range, is proposed. Finally, some conclusionsthat can be proved by Pspice analysis are given out about log-domain filters. Theinnovative points of this thesis include:1．Applying the original high-order filter design method to the design of high-order log-domain filters. A single-end 5-th log-domain filter and a differential 5-th order log-domain filter are realized in this dissertation as exmples；2．The noise problem is studied systematically and a kind of analysis method of high order log-domain filter is proposed. From such analysis the noise and dynamic range expressions of high-orderlog-domain filter are given out；3．The dynamic biasing technology is applied to the log-domain filters. And the change of the transfer function due to the use of dynamic biasing technology can be eliminated by differential method.