We designed 8-channel preamplifiers and multisite stimulation circuits on a 2:5 ×; 1:4mm2 chip using a 0.18 μm complementary metal-oxide-semiconductor (CMOS) process for a microelectrode array measurement system. The size of a 1-channel preamplifier including a DC store/adder circuit is 930 ×120 μm2. An 8-channel programmable stimulator was integrated on the same die. The preamplifier circuits can amplify a small neural signal with a low noise and a low power consumption (2 mW/ch) using a chopper operation. The stimulation circuits can apply a voltage of ±700mV to any channel and with any timing using serial digital data control. The performance of the biphasic stimulation waveform generated by the designed LSI chip is the same as that generated with a conventional stimulation system. These functions were confirmed by connecting the LSI chip to a conventional measurement system. The system miniaturization achieved using the custom LSI chip will offer great advantages in terms of future brain machine interface applications.
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