Minimization of offset of the tunable LP filters

Many tasks demand to improve the analog pre-processing dynamic range of various systems. Their pass-band is usually limited by low-pass (LP) filter. The tunable LP filters enable optimum choosing of cut-off frequency depending on the useful signal frequency range. On the other hand, the use of a tunable low-pass filter brings problems with increasing offset and drift. The survey of standard solutions of these problems is shown as well as the new solution to this problem. This new way consists in using crossover, which divides the frequency band to "DC" way and tunable pass-band. This structure enables to use any tunable LP filter without its influence on offset and drift.