CMOS Hall sensors consist of current-biased n-well plates that output magnetic-field dependent voltages. Offsets due to n-well inhomogeneity can then be suppressed by the spinning-current technique, which involves periodically rotating the direction of the biasing current and averaging the resulting output voltages. However, its effectiveness is limited by the JFET effect, which refers to the formation of a depletion region between the n-well and the p-type substrate due to the voltage drop across the n-well. This depletion region modulates the n-well resistance, and so is also a source of residual offset.

In this work, a CMOS Hall sensor is reported which employs voltage biasing and reads out the short-circuit Hall current. Compared to current biasing, this stabilizes the voltage drop across the n-well and significantly reduces the offset due to the JFET effect. Implemented in a standard 180nm CMOS process, the resulting sensor achieves a 3σ offset of 1.1μT with a noise floor of 60nT/√Hz. Compared to the state-of-the-art, these results represent a 3x reduction in offset, and a 5x improvement in resolution.

As electromagnetic waves cannot propagate sufficiently far in water, underwater communication is mainly performed using either acoustics or optics. However, none of these technologies have been proven to be completely effective in every situation. Therefore, research in new underwater communication systems can still bring large benefits to a wide range of different underwater technologies.
During this project, a promising new type of underwater communication system based on electric fields has been investigated. While two subgroups have been working on the characterization of the communication channel and different modulation techniques, this thesis focuses on the hardware needed for optimal communication. Moreover, this hardware includes both a low-noise receiver and a high power transmitter. An analysis of different design options, the detailed design of one of these options and the validation of the design are given in this report. However, to get a complete overview of the designed communication system and its performance, it is recommended to also read the other two thesis reports.