Class-D amplifiers are widely used in automotive audio systems because of their high efficiency. In modern car sound systems, multiple amplifiers are used to provide good audio effect. However, typical class-D amplifiers have a high idle-power, which can drain the battery quickly. To solve this problem, an ultra-low idle power class-D amplifier is proposed in this thesis. The simulation results show that this amplifier can achieve very low idle power while maintaining competitive linearity and efficiency.

This thesis describes the design of an ultra-low power temperature to digital converter. It is intended to monitor the excess heat produced during the wireless charging of implantable medical devices such as pacemakers. The TDC is designed to achieve an accuracy of ±0.1 °C (3 sigma) from 27 °C to 47 °C, and ±0.3 °C (3 sigma) from -40 °C to 85 °C after a 1-point trim. It also achieves a resolution of 0.01 °C at 10 Sa/s. The low power consumption (155 nW) is made possible by the implementation of a self-biasing BJT-core. Its low power consumption, accuracy, and resolution make it ideally suited for clinical temperature monitoring.

The availability of photolithography machines is key in the semiconductor industry, as downtime generally incurs in immense economic loss. Time to market is also very important for suppliers of photolithography systems, such as ASML. Photolithography machines include numerous measurement systems that are frequently used for qualification and troubleshooting, most of which are required during normal operation. Due to increased costs and complexity, it would not be practical to include dedicated sensors for every machine performance parameter relevant for diagnosis, therefore many parameters regarded as non-critical are not monitored. However, in some cases the information about the behaviour of these parameters can be very valuable to find the root cause of a failure or defect promptly. In these cases, a Wireless Sensor Network (WSN) would allow for a temporary installation of a measurement system to monitor such parameters.

This work presents the design of a WSN for monitoring the dynamics performance of the WaferHandler (WH), which is one of the major subsystems of a photolithography machine. The scope of the project includes:

• The selection of a radio technology on which the network is based on.
• The hardware design of a wireless sensor node for measuring acceleration, based on commercial off-the-shelf (COTS) components.
• The identification and firmware implementation of key principles in which the communication protocol should be based on according to the requirements of the application.
• The estimation of the power consumption and lifetime of the network.
• The design and execution of experiments to assess the reliability of the proposed solution.

Among the requirements of the system, the size of the sensor nodes, the network synchronization accuracy, and the maximum power dissipation stand out as the main challenges. As the available space inside the WH is very scarce, the sensor nodes must have a compact form factor to fit in the locations where they are meant to be installed. The reliability of the system is greatly determined by its capacity to remain synchronized with relatively high accuracy during a measurement. This can be difficult to achieve in a harsh environment such as the inside of a machine, where interference and signal fading are expected to recurrently cause the loss of packets used for network synchronization.Packet re-transmission should not be abused to alleviate the problem, as the sensor nodes are required to operate in vacuum and overheating can become a problem.

This work focuses on addressing the fundamental limitation on the minimum cold start-up voltage that could be harvested from a thermoelectric element (TEG) for human-body wearable applications. For ultra-low DC voltages, the challenge translates to generating a timed-signal to amplify it up to a value that could be used to drive, say, a boost converter which can then start-up the entire energy module. Contemporary works have, thus, strived to accomplish this using a charge-pump-based or a transformer-based approach, which in turn imposes a limit on the minimum TEG voltage that can be harvested. The solution this work proposes is to decouple the Cold Start-up system from the TEG altogether and instead, use a piezoelectric element (PEH). This element being capable of producing a well-timed (AC) signal for free, based on human body vibrations, can potentially drive a boost converter. To this end, an integrated circuit (IC) is designed that can utilize the voltage from the PEH, amplifying it up to generate a well-controlled signal that could operate the boost converter. At the heart of this IC, is a self-reconfigurable charge pump that arranges its stages in different boosting ratios (without any complex logic or DSP) based on the input voltage, to allow for a maximum harvested power. The proposed self-reconfigurable architecture can potentially lead the charge pump to be load-variation-resistant. It achieves this by providing an almost constant voltage while increasing the power for higher load demands, at the same time maintaining a constant efficiency. Thus, the fully on-chip implementation in TSMC 0.18 um CMOS, can cold start-up the system from 25 mV of thermoelectric voltage to deliver an output voltage of 1 V at 56.5 % converter efficiency, consuming only 240.5 pW of dynamic power (simulation). The minimum Cold Start-up voltage and dynamic power were found to be 18 mV (ΔT = 0.1 K) and 231.6 pW respectively, to supply 1 V at 44 % converter efficiency. Moreover, in order to prove that the fundamental limitation on the Cold Start-up voltage has been addressed successfully, the IC was also simulated to check whether it can further be lowered. In this case, by providing a piezoelectric excitation voltage 73.3 mVRMS higher, the Cold Start-up voltage was found to be reduced to 15 mV to supply a constant 1 V at the load. It was also found that increasing the inductor value in this case, can also allow the energy module to support even lower Cold Start-up voltages.

This work presents a fully differential Class D audio amplifier using 2.1MHz pulse-width modulation (PWM) frequency and 425kHz LC filter cut-off frequency to decrease the cost of off-chip components. Moreover, feedback after LC filter structure is used to attenuate LC filter nonlinearities.