For my sensor application I need a 2nd low pass filter with a voltage controlled cut off frequency. The range of operation for the cut off frequency is 5kHz to 5Mhz or 10kHz to 10MHz, fixed Q (complex poles would be nice) and DC offset is not a problem.
Does anybody have some ideas, topologies, tricks or app-notes which might lead to a compact solution. Solutions with variable gain amplifiers are welcome. Solutions with gm-c filters (from Sánchez-Sinencio) are less implementable I think because of the limited availability of OTA's or diamond transistors.
Thanks in advanced,