A 48 nW, Universal, Multi-Mode Gm-C Filter with a Frequency Range Tunability

This paper presents an ultra-low-power, inverter-based, universal Gm-C filter capable of operating in multiple modes: voltage, current, transconductance, and trans-resistance. The proposed filter features orthogonal tunability of the center frequency (ω0) and quality factor (Q). To achieve ultra-low power consumption, all transistors are biased in the subthreshold region with a supply voltage of 0.5 V. A Nauta inverter-based gm block is utilized as the operational transconductance amplifier (OTA), further enhancing power efficiency. The filter is capable of generating all filtering responses across a supply voltage ranges from 1.2 V down to 0.5 V. Moreover, the center frequency and quality factor can be tuned by adjusting capacitance values. The proposed Gm-C filter achieves a power consumption of 48 nW, with the center frequency ranging from 50.6 Hz to 1270 Hz.