Tunable BiCMOS continuous-time filter for high-frequency applications

A BiCMOS fully differential transconductor based on MOS transistors operating in the linear region is presented. The circuit has an equivalent nondominant pole located above 1.5 GHz. This makes it suitable for high-frequency continuous-time filters. A second-order low-pass filter using the new transconductor realized in a 2- mu m BiCMOS technology is reported. The cutoff frequency f/sub 0/ of the cell is tunable in the range of 8-32 MHz and the quality factor is 2. The filter THD stays lower than -40 dB for an output signal up to 3.2 V/sub p-p/ at 5-MHz frequency. The area of the cell is 0.322 mm/sup 2/ and the power consumption (with f/sub 0/=25 MHz) is 30 mW with a single 5-V power supply.<
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