Design of log domain low-pass filters by MOSFET square law

In this paper, the log domain low-pass filter based on the MOSFET square law is proposed. This approach demonstrates that the cutoff frequency of the low-pass filter is not only attainable at megahertz frequencies but also tunable electronically. In addition, implemented by current-mode square-root circuit blocks, current mirrors and capacitors, the proposed low-pass filter can be operated with a 3.3 V power supply voltage. The proposed circuit has been simulated in 0.35 /spl mu/m CMOS technology, and the simulation results show that the proposed circuit has the merits of high frequency operation, tuneability, low power supply voltage operation.