Two preamplifiers for non-invasive on-chip recording of neural-signals

This paper presents two preamplifier designs suitable for non-invasive recording of action potential from neurons grown on pads immersed in a biocompatible electrolyte. The pads are either aluminum or, after post-processing, porous silicon. The first preamplifier is built around a CMOS-differential stage and features high input impedance. The second amplifier employs lateral pnp transistors in the input stage. This amplifier has relatively low input impedance and is suitable for interfacing the neurons grown on porous silicon. A cost effective 0.8μm standard CMOS technology has been used throughout. A chip micrograph and preliminary measured results, prior to neuron growth, are included.