A switched-capacitor neural preamplifier with an adjustable pass-band for fast recovery following stimulation

For extracellular recordings from neurons, it is desirable to use the same electrode for stimulation as well as for recording. Since neural preamplifiers usually exhibit high-pass filtering at frequencies as low as 0.1 Hz, the recovery from saturation is typically very slow. Consequently, following stimulation, no signal can be detected for up to several seconds. This is unacceptably slow response of the preamplifier because the majority of neurons fires action potentials within first milliseconds following stimulation. Here we propose to use a switched-capacitor preamplifier with adjustable pass-band for fast recovery from saturation caused by stimulation via the recording electrode. The idea was tested in a real preamplifier manufactured with a standard CMOS technology (0.35 microm). In control conditions, the high-pass filter was set to 100 Hz and, during stimulation, was shifted to 10 kHz. Such a shift allows the reduction of the recovery time from tens of milliseconds to sub-millisecond range.