Low-Power Widely Tunable Gm-C Filter Employing an Adaptive DC-blocking, Triode-Biased MOSFET Transconductor

We propose a transconductor capable of providing a wide continuous-tuning-range filter applicable to Bluetooth, W-CDMA, LTE, and IEEE 802.11a/b/g W-LANs without sacrificing power consumption or die area. The wide tuning range is achieved without the need for any array configuration, using triode-biased input MOSFETs with transconductance that is widely tunable by means of drain bias adjustment. The transconductor also uses an adaptive DC-blocking circuit that suppresses bias current in a high transconductance mode, which results in minimizing transconductor power consumption.A 4th-order Butterworth low-pass filter using this transconductor, fabricated in a 0.18-μm CMOS process, exhibits a cut-off frequency tuning range of 0.3-12 MHz with a current consumption of 0.6-2.6 mA. The die area is small: 0.125 mm².