| Summary: | This paper presents the operation principle and the silicon characterization of a power efficient ultra-low voltage and ultra-low area fully-differential, digital-based Operational Transconductance Amplifier (OTA), suitable for microscale biosensing applications (BioDIGOTA). Measured results in 180nm CMOS prototypes show that the proposed BioDIGOTA is able to work with a supply voltage down to 400 mV, consuming only 95 nW. Owing to its intrinsically highly-digital feature, the BioDIGOTA layout occupies only 0.022 mm<sup>2</sup> of total silicon area, lowering the area by <inline-formula> <tex-math notation="LaTeX">$3.22\times $ </tex-math></inline-formula> times compared to the current state of the art, while keeping reasonable system performance, such as 7.6 NEF with <inline-formula> <tex-math notation="LaTeX">$1.25~\mu V_{\mathrm {RMS}}$ </tex-math></inline-formula> input referred noise over a 10 Hz bandwidth, 1.8% of THD, 62 dB of CMRR and 55 dB of PSRR.
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