A 4.6mW, 22dBm IIP3 all MOSCAP based 34–314MHz tunable continuous time filter in 65nm

Abstract

A inverter based filter design is proposed that uses only MOSCAPs as filter capacitors. Further in the design the load capacitance compensates the negative feedback network allowing the majority of current to flow into the load. This results in an increase in the overall power efficiency. As a proof of concept, a 3rd order inverter based 34-314 MHz tunable continuous time channel select filter for software-defined radios is fabricated in TSMCs 65nm technology. By using the high density tunable MOSCAPs at a low swing node, the filter achieves an OIP3 of +25.24 dBm while drawing 4.2mA from a 1.1V supply and occupies an area of 0.007mm2. The measured intermodulation distortion varies by 5dB across a 120° variation in temperature and 6.5dB across a 200mV variation in power supply. Further, the filter presents a high impedance node at the input and a low impedance node at the output easing system integration.