Low noise amplifier with active feedback structure for implantable neural recording

Abstract

A novel low-power, low-noise amplifier is described for biomedical and bioengineering brain neural recording applications. The bioamplifier achieves the best power-size tradeoff compared to the previous design. By means of a new active feedback configuration, the DC offset is rejected without the large capacitors. An active differentiator with an amplifier in the feedback path places a high-pass cutting frequency in the transfer function. The midband gain consists of the passive components, and is insensitive to the mismatch of process. The bioamplifier has been implemented in the 0.35-μm 2P4M CMOS process and occupies 0.052 mm 2 of die area. The current consumption of amplifier is 2 μA at ±1.5 V supply. The bioamplifier achieves a midband gain of 42 dB and a −3 dB bandwidth from 13 Hz to 10.5 kHz. The input-referred noise is 5.7 μV rms corresponding to an NEF of 3.1.

A 0.1–8 GHz wideband low-noise amplifier exploiting gain-enhanced noise-cancelling technique

“…However, there are always trade-offs between all these requirements, which cannot be very well satisfied simultaneously. For example, the shunt-shunt resistive feedback [1], common-gate (CG) [2], and positive active feedback network [3] can achieve good input matching in a relatively wide frequency range. However, they all have the problems of large NF and insufficient gain.…”