info:eu-repo/semantics/article
A current-reuse biomedical amplifier with a NEF < 1
Fecha
2018-05Registro en:
Miguez, Matías R.; Gak, Joel; Arnaud, Alfredo; Oliva, Alejandro Raul; Julian, Pedro Marcelo; A current-reuse biomedical amplifier with a NEF < 1; Springer; Journal Of Analog Integrated Circuits And Signal Processing; 95; 2; 5-2018; 283-294
0925-1030
1573-1979
CONICET Digital
CONICET
Autor
Miguez, Matías R.
Gak, Joel
Arnaud, Alfredo
Oliva, Alejandro Raul
Julian, Pedro Marcelo
Resumen
Noise Efficiency Factor (NEF) is the most employed figure of merit to compare different low-noise biomedical signal amplifiers, taking into account current consumption, noise, or bandwidth trade-offs. A small NEF means a more efficient amplifier, and was assumed to be always NEF > 1 (an ideally efficient single BJT amplifier). In this work current-reuse technique will be utilized to exceed this limit in a very efficient CMOS amplifier. A micro-power, ultra-low-noise amplifier, aimed at electro-neuro-graph signal recording in a specific single-channel implantable medical device, is presented. The circuit is powered with a standard medical grade 3.6 V(nom) secondary battery. The amplifier input stage stacks twelve differential pairs to maximize current-reuse. The differential pair stacking technique is very efficient: allows most of the energy to be dissipated in the input transistors that amplify and not in mirror or bias transistors, and allows also the input transistors to operate with a reduced VDS just above saturation. The amplifier was implemented in a 0.6 μm technology, it has a total gain of almost 80 dB, with a 4 kHz bandwidth. The measured input referred noise is 4.5 nV/Hz1/2@1 kHz, and 330 nVrms in the band of interest, with a total current consumption of only 16.5 μA from the battery (including all the 4 stages and the auxiliary circuits). The measured NEF is only 0.84, below the classic NEF = 1 limit.