A 5th order gm-C low-pass filter with ±3% cut-off frequency accuracy and 220MHz to 3.3GHz tuning-range in 28nm LP CMOS

A 5th order gm-C filter complete with calibration circuits with wide tuning range and cut-off frequency up to the GHz range is presented. To simplify calibrations, integrators are designed to have a relatively low static gain of 32dB, regulated with negative resistors. Transconductance and gain are continuously controlled with a master-slave approach leading to a remarkably stable filter shape and cut-off frequency accuracy within ±3% over a 0°-100° temperature range and ±5% supply variation. A test-chip has been realized in a 28nm Low Power CMOS technology. The cut-off frequency is tunable from 220MHz to 3.3GHz with power dissipation scaling from 5mW to 30mW. THD is -40dB at -24dBV input signal while the integrated input equivalent noise is lower than 400μVrms, corresponding to an SNR better than 39dB.