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 amplification (TIA) circuit followed by adjustable cut-off frequency and a low-pass filter (LPF) was implemented 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-bandwidth 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/√HzQUOTE√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 technology.
Highlights
Near-Infrared Spectroscopy System (NIRS) is a new medical device that can be used for monitoring and in several neurological diseases in the human brain
The NIRS system consists of near light sources, photo detectors, an amplifier followed by a filter in data acquisition system and a process unit
We present the transimpedance amplifier (TIA) followed by a low-pass filter, which are forming the front-end of the data acquisition system of a typical NIRS receiver
Summary
NIRS is a new medical device that can be used for monitoring and in several neurological diseases in the human brain. The NIRS acquisition channel contains an avalanche photodiode connected to the input of a preamplifier called a transimpedance. It plays a critical role in determining the numerous receiver aspects in term of performances and sensitivity. We present the transimpedance amplifier (TIA) followed by a low-pass filter, which are forming the front-end of the data acquisition system of a typical NIRS receiver. To minimize the effectiveness of the parasitic capacity at the receiver input several CMOS circuit techniques have been proposed, including the regulated cascode topology configuration [16] [17] The drawbacks of these topologies are mainly in the input noise and the TIA gain performance. We focused on the TIA and LPF as two interesting electronic components for decrease the noise in preamplifier stage
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