A SWITCHED CAPACITOR BASED TRANSIMPEDANCE AMPLIFIER FOR DETECTION OF HAB THROUGH OPTICAL SENSING

Abstract

In the recent years, there has been a substantial increase in the manifestation of harmful algal blooms. A certain species called cyanobacteria that is commonly present in freshwater bodies are found to release a class of deadly toxins known as microcystin. This toxin poses a threat to humans and wildlife since they can cause severe illness or even death on consumption of contaminated water. Traditional sampling methods are essentially lab based detection methods that are inconvenient and demands extensive manual effort. Hence, large-scale occurrence of harmful blooms in water resources demands the development of efficient and reliable methods for monitoring and detection of harmful algal blooms through remote sensing In this thesis work, an optical sensing readout circuit has been discussed for a lab-on-chip system that can remotely detect and report the presence of a deadly toxin known as microcystin-LR released by a species of harmful algal bloom. Since a transimpedance amplifier is an integral block of the optical sensing readout circuit, a low power, low noise switched capacitor based transimpedance amplifier design has been proposed for the optical sensing readout circuit. It has been designed in cadence using an operational amplifier and a logic control circuit in 0.18um CMOS technology. The simulated results of the proposed design show a low power consumption of 7.2uW with a high transimpedance gain of 121.3 dB ohm. A low input referred noise of 65.59fA/(square root) of HZ could also be achieved through correlated double sampling. This design is more compact, less noisy and less power consuming as compared to existing architectures and thus is best suited for the portable optical sensing system for detection of harmful algal blooms.