All MOSCAP Based Continuously Tunable Filter

This chapter presents an inverter based filter design that uses only MOSCAP 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 third order inverter based 34–314 MHz tunable continuous time channel select filter for software-defined radios is fabricated in TSMC’s 65 nm technology. By using the high density tunable MOSCAPs at a low swing node, the filter achieves an OIP3 of +25.24 dBm while drawing 4.2 mA from a 1.1 V supply and occupies an area of 0.007 mm². The measured intermodulation distortion varies by 5 dB across a 120^∘ variation in temperature and 6.5 dB across a 200 mV 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.