Project of a bandgap voltage reference and a temperature sensor for "energy harvest" systems

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e Computadores

The objective of this thesis is to study the behaviour of a bandgap voltage reference and develop it in order to be more efficient than the existing ones. In this case having applicability in energy harvest, the main approach for this circuit is to reduce the power dissipation and at the same time guarantee a stable of the reference voltage. This can be achieved through the utilization of MOS transistors which can work with a lower voltage then bipolar transistors. The reference voltage circuit present in this thesis can work with a supply voltage as low as 500 mV. In energy harvest systems besides the need to work with extremely low voltages, the sensitivity of the signals is very high, to temperature variation. So it was also important to work with an extended ranges of temperature. For this work it was also developed a temperature sensor so that it has applicability in various fields. The sensor works by currents generated by the bandgap voltage reference, having similar results to a dual slope integrating analogue-to-digital converter, although its operation and logic are quite different. The proposed solution is to implement a reference voltage generator powered by a voltage source of 500 mV, with a consumption of about 7 W. Having a temperature coefficient slightly below 74 ppm/ C and a temperature sensor with linearity quite satisfactory.