A lowpower classAB GmC biquad stage in CMOS 40nm technology A lowpower classAB GmC biquad stage has been designed using a voltage buffer based on error amplifiers and a pushpull current mirror. The classAB architecture allows good power efficiency by lowering the required bias current. The biquad stage consumes  250boldsymbolmu mathbfA  from a 1.2V supply, and achieves a resonance frequency of 2.2MHz with a Q of 2. The SFDR (spuriousfree dynamic range) with a twotone test is 48dB and the SNR (signaltonoise ratio) is 44.4dB, with a 400mVpp differential input signal. A pseudodifferential architecture allows large bandwidth and lower power consumption in the transconductance stages. The stage can be used to synthetize lowpass and bandpass filters composed of lowQ stages.

A Subthreshold FoldedCascode Lowpass Biquad for Biopotential Acquisition This paper presents a subthreshold CMOS 2ndorder lowpass filter for lowfrequency biomedical signals discrimination. We modify the foldedcascode (FC) OTA to combine with two floating capacitors in a unitygain negative feedback configuration. Circuit simulation using 0.35 xcexbcm CMOS confirms that the proposed biquad, operated from a 1 V dc supply, consumes 15.15 nW to obtain a cutoff frequency of 152 Hz. With 52.5 pF total capacitance, the filter contributes an inputreferred noise of 31.6 xcexbcV rms . At cutoff frequency, when a 100 mV pp  sinusoidal input signal is applied, the filter produces 1.7% total harmonic distortion. This results in a filteru0027s dynamic range of 61 dB.