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A Low Distortion Continuous Time Sigma Delta Modulator using a High Input Impedance Instrumentation Amplifier for Neural Recording

: Nikas, A.; Jambunathan, S.; Klein, L.; Voelker, M.; Ortmanns, M.


Institute of Electrical and Electronics Engineers -IEEE-; IEEE Circuits and Systems Society; IEEE Engineering in Medicine and Biology Society -EMBS-; IEEE Solid-State Circuits Society:
BioCAS 2018, Biomedical Circuits and Systems Conference. Conference Proceedings : Advanced systems for enhancing human health; Cleveland, Ohio, USA, October 17-19, 2018
Piscataway, NJ: IEEE, 2018
ISBN: 978-1-5386-3604-6
ISBN: 978-1-5386-3603-9
4 S.
Biomedical Circuits and Systems Conference (BioCAS) <2018, Cleveland/Ohio>
Fraunhofer IIS ()

In this paper an architecture for a continuous time sigma delta modulator used in a neural recording channel is proposed. The instrumentation amplifier based input structure of the converter exhibits a high input impedance and linear behavior. Properties making its use interesting in analog frontends for direct application on sensor elements. Circuit linearity is achieved solely by negative feedback. A prototype was developed as a 2 nd order single bit modulator in a cascade of integrators feedforward form and was taped-out in a 180nm technology. Simulations show an input impedance of >1GΩ and a THD of 0.012%. The input referred noise is 2.2μV at an average current consumption of 14μA occupying an area of 0.07mm2.