CMOS amperometric sensors with a microelectrode array offer great potential for counting bacteria because of their low cost, compact size, and ease of use. This paper presents a current-integration-based CMOS amperometric sensor for high-sensitivity bacteria counting. It has a current integrator for noise reduction and reportedly the most large-scale microelectrode array (1024 × 1024). This proposed sensor can count the number of bacteria ranging from a single cell to approximately a million cells. A prototype chip was fabricated using two-poly three-metal (2P3M) 0.6-µm standard CMOS technology. A 7.6 × 7.1-mm2 chip operates from a 5V supply at 1.9mA. In addition, by using the prototype chip, we performed electrochemical measurement and partial 2D imaging of silicone through constant potential amperometry. The measurement results indicate that the proposed sensor chip was able to accurately readout redox current from the 1024 × 1024 sensor array.

A high-gain, low-noise amplifier for microelectrode probe, which integrated multimicroelectrode array for extracellular recording of neural activities and solid state circuits for the amplification of induced signals from the electrodes onto one substrate, was fabricated. In the amplifier, low-noise MOSFETs are used in the first stage, an interstage high-pass filter is incorporated to avoid saturation of the amplifier due to the polarization voltage of the electrode. In the second stage, an operational amplifier incorporating Bi-MOSFETs for the realization of high input impedance and large gain-bandwidth product is used. The gain of the fabricated amplifier is 56 dB for the frequency range between 2 Hz to 10 kHz, the noise voltage is 20µVpp; these satisfied design specifications.