A Method for Continuous Tuning of MOSFET–RC Filters with Extended Control Range

In this paper a tuning structure for a MOSFET?RC filters is presented. The proposed tuning structure is composed of switched resistor banks with voltage controlled transistors. The voltage controlled transistors use active feedback with extended control range for continuous filter parameter tuning, without degrading the total linearity performance of the filter. The proposed tuning structure is tested by implementing it in a second order low pass biquadratic filter cell in 65 nm CMOS technology. The designed filter has a highly reconfigurable response, ranging from Chebyshev to Bessel, a tuneable -3 dB bandwidth from 10 MHz to 100 MHz and can be used for multiple standard wireless solutions. Filter IIP3 performance is not degraded when the bandwidth is continuously tuned by 40 % with a 1 V pp input. The maximum power dissipation, including active feedback circuits, is 17.2 mW from a 1.2 V source when the filter is tuned to 100 MHz bandwidth.