Design and measurements of 64-channel ASIC for neural signal recording

Abstract

This paper presents the design and measurements of a low noise multi-channel front-end electronics for recording extra-cellular neuronal signals using microelectrode arrays. The integrated circuit contains 64 readout channels and was fabricated in CMOS 0.18 microm technology. A single readout channel is built of an AC coupling circuit at the input, a low noise preamplifier, a band-pass filter and a second amplifier. In order to reduce the number of output lines, the 64 analog signals from readout channels are multiplexed to a single output by an analog multiplexer. The chip is optimized for low noise and matching performance with the possibility of cut-off frequencies tuning. The low cut-off frequency can be tuned in the 1 Hz-60 Hz range and the high cut-off frequency can be tuned in the 3.5 kHz-15 kHz range. For the nominal gain setting at 44 dB and power dissipation per single channel of 220 microW the equivalent input noise is in the range from 6 microV-11 microV rms depending on the band-pass filter settings. The chip has good uniformity concerning the spread of its electrical parameters from channel to channel. The spread of gain calculated as standard deviation to mean value is about 4.4% and the spread of the low cut-off frequency is on the same level. The chip occupies 5x2.3 mm(2) of silicon area.

Tuning the low cut-off frequency in multichannel neural recording amplifiers by the on-chip correction DACs

“…In order to clarify this phenomenon we simulated the effective channel resistance of the PMOS transistor versus its gate -source voltage. The simulated transistor is chosen to be the same as in our former design [12]. It has a threshold voltage equal to 0.5 V while its channel dimensions are equal to W/L = 0.4 µm / 300 µm (CMOS 180 nm technology).…”

“…In the first approach called Option A (see Fig. 1 a)) and reported for example in [12,13] two separated blocks are used: CR high pass filter and differential amplifier AMP. The separation of these blocks gives one possibility to set in the system the low cut off frequency and the voltage gain separately.…”

Comparision of two different architectures of multichannel readout ASICs for neurobiological experiments

“…Based on our experience [6,7,8,9] we decided to design a multichannel systems for recording neurobiology signals in submicron 180 nm CMOS technology. We chose two different architectures of recording channels and these designs are presented below.…”

64 Channel ASIC for Neurobiology Experiments

“…Based on our experience in design and practical applications of such kind of ASICs for recording systems comprising of hundreds of electrodes [6], [7], [8] we propose a new 64-channel ASIC, which meets the above requirements.…”