This study presents a new low‐voltage and low‐power, mixed‐mode, universal Gm‐C filter capable of generating simultaneous filtering outputs. The proposed circuit employs only 19 inverters as operational transconductance amplifiers, and 2 grounded capacitors in carbon nanotube field‐effect transistor (CNTFET) technology. However, due to the proper use of subthreshold transistors biased at ±0.25 V supply, the power consumption of the proposed circuit is reduced effectively. Furthermore, as the HSPICE simulation results show, the proposed filter consumes only 11.66 µW of power, while its total harmonic distortion is obtained −55.4 dB at 100 MHz centre frequency. Moreover, the input referred noise values at 100 MHz are reduced to 11.57 nV/ and 760 fA in voltage and current modes, respectively.

A circuit with a low-power low-noise amplifier and a Gm-C ultra-low-power filter is proposed in this paper for portable electroencephalogram (EEG) acquisition applications. The proposed circuit contains a two-stage chopper-stabilized fully recycling folded cascode (TSRFC) amplifier and a second-order continuous-time Gm-C low pass filter (LPF) with ultra-low-power consumption. The noise and input offset are reduced using the chopper-stabilized technique. A two-stage amplifier that consists of composite transistors and a recycling structure is proposed for the amplifier. Compared to a typical folded cascode CMOS amplifier, the proposed design has higher DC gain and slew rate as well as lower input-referred noise. This circuit has an adjustable second-order Gm-C LPF with very low power consumption. The amplifier achieves a midband gain of 70 dB and a -3dB bandwidth in the range 0.1-212 Hz. Moreover, the amplifier is designed in 0.18-μm CMOS process and the chip area of the proposed circuit with pads is 450×450 μm2. The adjustable LPF has a 100 Hz cut-off frequency. The proposed circuit has an input-referred noise of 0.7 μVrms, (0.1~100Hz) and a power consumption of 380 nW at 1 V supply.