Low Power Analog Circuit Design and Radio Frequency Circuits for Biomedical Applications

Abstract

In the last few years, implantable medical devices are being used for the treatment of a growing number of pathologies. Implantable medical devices are sophisticated electronic circuits that are implanted into the body to restore or improve various body functions in patients. These devices can perform a range of tasks including sensing, control, and stimulation, which enables them to monitor and regulate the health of the patient. The electronics of a general biomedical device typically consist of several subsystems that work together to perform the desired functions. For example, energy delivery subsys-tem, analog-to-digital conversion subsystem, signal processing subsystem, communication subsystem. The stringent energy constraints dominate the design of biomedical systems. Additionally, systems powered through energy harvesting must be able to work with lower supply voltages. Low power consumption, low supply voltage and accuracy are few of the most important parameters for bio-implants. With all these constraints in play, we have put efforts to design current reference and voltage reference as they are present in almost every analog and mixed signal system. Efforts were put to design a low power current reference with high line sensitivity using peaking current sourceby exploiting the back-gate effect of a MOSFET in subthreshold region. The design works from a 0.55V supply voltage and generates a reference current of 5.6nA. A low line sensitivity of 0.022%/V is achieved and the design works for a temperature range of 0-80◦C. This current reference showsthe best result of line sensitivity among the previous state-of-the-art works. Consequently, we have come up with a switched capacitor network-based bandgap voltage reference (BGR) circuit designed to achieve high accuracy and low power consumption for implantable biomedical applications. A low- power clock generator circuit is proposed, to reduce the leakage current thereby reducing the circuit’s power consumption to 18.5nW at typical conditions. The design works from a supply voltage of 0.5V and has a TC of 74.5ppm/◦C over a temperature range of 0-80◦C. Lastly, we have expanded our research to the field of RF circuits for biomedical applications. An on-chip Vector Network Analyzer (VNA) isdesigned to detect a biomolecule for medical diagnosis. This technique, known as RF sensing, can be used to detect changes in the dielectric properties of a sample, which can indicate the presence of certainbiomolecule. In this part of the research, various blocks of the onchip VNA is demonstrated and the future scope of this work is explained.