In this paper, a low-power and precise electrical stimulator is introduced in which no operational amplifier (OPAMP) is used. For electrical stimulations that have low pulse width, an OPAMP with high slew rate is needed which is power consuming. In this work, the OPAMP is substituted with a digital circuitry. A 100 KHz clock is also used to update the current of the stimulator in the stimulation phases in order to make the stimulator accurate enough. Producing such a clock needs only few micro watts. This stimulator is simulated in a 0.18 μm CMOS process, as well. The simulation results shows that this stimulator has only 0.056% charge mismatch in 1 mA stimulation current with a pulse width of 32 μs.

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Closed-loop implantable electronics offer a new trend in therapeutic systems aimed at controlling some neurological diseases such as epilepsy. Seizures are detected and electrical stimulation applied to the brain or groups of nerves. To this aim, the signal recording chain must be very carefully designed so as to operate in low-power and low-latency, while enhancing the probability of correct event detection. This paper reviews the electrical characteristics of the target brain signals pertaining to epilepsy detection. Commercial systems are presented and discussed. Finally, the major blocks of the signal acquisition chain are presented with a focus on the circuit architecture and a careful attention to solutions to issues related to data acquisition from multi-channel arrays of cortical sensors.