A Very Low SEF Neural Amplifier by Utilizing a High Swing Current-Reuse Amplifier

Although current-reuse amplifier has been widely used in biomedical applications because of their low input-referred thermal noise, they don’t have high output swing and their gain is limited. In this article, a rail-to-rail current-reuse amplifier with a 92 dB open-loop gain is introduced while its power and noise increment is just 7%. The proposed structure is a two stage amplifier which doesn’t need further compensation since all nodes are diode connected except for the output node. In order to show the merit of the proposed structure, the NEF, PEF and SEF of the proposed amplifier in a capacitively-coupled neural amplifier structure is compared to the state-of-the-art neural amplifiers. The amplifier is designed and simulated in a commercially available 0.18 µm CMOS technology. The midband gain of the neural amplifier is 40 dB in the bandwidth between 0.6 Hz and 5 kHz. The proposed structure consumes 1.07 µA current from a 1.2 V supply voltage. The NEF, PEF and SEF of proposed structure are 1.68, 3.4, 0.05, respectively. The total area consumption of the neural amplifier is 0.03 mm2 without pads.

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