A Widely Tunable Bandpass CMOS Filter Based on a Low-Voltage Active Inductor

Abstract

A Chebyshev bandpass filter for digital TV (DTV) tuner ICs, as an RF tracking filter, based on a low-voltage tunable active inductor (TAI) is presented. The new filter has a tuning range of 200–800[Formula: see text]MHz. Independent tuning of the inductance and central frequency of the filter are very important in this wide frequency span. Adjusting the inductance for tuning of the filter should not vary its quality factor and consequently performance of the filter. Use of a feedback resistor in the active inductor makes the inductance and quality factor tuning-independent. Moreover, the feedback resistor increases the quality factor of the active inductor. Biasing the bulk terminals of the devices to a positive voltage, we achieve low threshold devices and consequently low voltage TAI. The proposed filter has IIP3 and noise figure of [Formula: see text]0.8 to 9.5[Formula: see text]dBm and 19.1 to 20.9[Formula: see text]dB, respectively. Besides, the power consumption varies from 9.6 to 25.5[Formula: see text]mW in the tuning range of 200–800[Formula: see text]MHz.