A low-noise fully-differential CMOS preamplifier for neural recording applications

A fully-differential bandpass CMOS preamplifier for extracellular neural recording is presented in this paper. The capacitive-coupled and capacitive-feedback topology is adopted. We describe the main noise sources of the proposed preamplifier and discuss the methods for achieving the lowest input-referred noise. The preamplifier has a midband gain of 43 dB and a DC gain of 0. The -3 dB upper cut-off frequency of the preamplifier is 6.8 kHz. The lower cut-off frequency can be adjusted for amplifying the field or action potentials located in different bands. It has an input-referred noise of 3.36 mu Vrms integrated from 1 Hz to 6.8 kHz for recording the local field potentials (LFPs) and the mixed neural spikes with a power dissipation of 24.75 mu W from 3.3 V supply. When the passband is configured as 100 Hz-6.8 kHz for only recording spikes, the noise is measured to be 3.01 mu Vrms. The 0.115 mm(2) prototype chip is designed and fabricated in 0.35-mu m N-well CMOS (complementary metal oxide semiconductor) 2P4M process.