This lecture covers the design of CMOS circuits for metabolites detection in fixed-voltage electrochemical cells, focusing on basic configurations, voltage driving needs, operational amplifier features, and the risk of saturation. It also discusses the use of grounded counters, working electrodes, and references, as well as the importance of temperature compensation in biosensors. The lecture explores various topologies for current measurement, multiplexing techniques, and resistance-to-pulse-width converters, emphasizing linearity and CMOS mismatch effects.