Circuits and Systems, 2014, 5, 191-200 Published Online August 2014 in SciRes. http://www.scirp.org/journal/cs http://dx.doi.org/10.4236/cs.2014.58021 How to cite this paper: Chaddad, A. (2014) Low-Noise Front-End Receiver Dedicated to Biomedical Devices: NIRS Acquisi- tion System. Circuits and Systems, 5, 191-200. http://dx.doi.org/10.4236/cs.2014.58021 Low-Noise Front-End Receiver Dedicated to Biomedical Devices: NIRS Acquisition System Ahmad Chaddad University of Texas MD Anderson Cancer Center, Houston, USA Email: Achaddad@mdanderson.org Received 15 June 2014; revised 20 July 2014; accepted 2 August 2014 Copyright © 2014 by author and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract This paper concerns the design and the implementation of a fully integrated front-end intended to Near-Infrared Spectroscopy System (NIRS) acquisition system. A low-noise transimpedance ampli- fication (TIA) circuit followed by adjustable cut-off frequency and a low-pass filter (LPF) was im- plemented in order to decrease noise circuit of NIRS detectors. For TIA, a single ended common source, common gate input stage based on a cascode structure is used to get a higher gain-band- width closed-loop transimpedance amplifier. To enhance the circuit noise performance, a single feedback transistor technique is used, compared to passive feedback, to achieved high quality data from NIRS acquisition channel. The proposed LPF combines two control methods to adjust the low cut-off frequency. Simulation results show a TIA gain of 104.2 dBΩ, −3dB bandwidth of 19 MHz and an equivalent input noise current spectral density of 446 fA/√Hz. LPF filter exhibits a relatively constant noise 201nV/√Hz from 0 Hz to 700 KHz and linearity performance over its entire tuning range. The proposed front-end of NIRS preamplifier is implemented using 0.18 µm CMOS technol- ogy. Keywords NIRS, TIA, LPF, CMOS 1. Introduction NIRS is a new medical device that can be used for monitoring and in several neurological diseases in the human brain. It is considered in many hospitals for brain functional imaging. Among the most used methods in the clinical setting is functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) [1]