A Very Low Power Bandpass Filter for Low-if Applications

Abstract

This paper presents a second-order bandpass filter for IF frequencies in the range of 500 kHz–2 MHz. By using a single Gm–cell as a biquad filter, considerable saving in area and power is feasible. Higher order structures can be achieved by cascading this second-order block. This Gm-C filter achieves a dynamic range of 37 dB for 1% IM3 in Bluetooth while dissipating only 10.5 mW from 3.3 power supply in 0.35 μm CMOS process. The on-chip indirect automatic tuning circuit sets the filter center frequency to an external reference clock.

On Design of Self-Tuning Active Filters

“…Applications of these filters involve frequency of operation from a few tens of hertz up to gigahertz [1]. OTA-C filters offer many advantages over other continuous-time filters in terms of low power and high frequency capability [2]. They are used for applications such as selective amplifiers, IF and RF filters [1][2][3][4], filters for high-speed baseband data links [5], equalizers for bit detectors in magnetic and optical disk recording [5], medical electronics [6,7], video signal processing [8], phase synchronizers [9], image-rejection in super-heterodyne receiver [10], etc.…”

“…Analog filters are also tuned by master-slave tuning schemes [2]. The most commonly used master-circuit is voltage-controlled oscillator (VCO), whereas a slave filter is built with identical integrators.…”