A Comparative Study of Voltage Reference Generation Techniques for Low-Voltage Micropower Management Circuits

In this paper, a comparative analysis is performed between two techniques previously presented in the literature for generating voltage references ($V_{R E F}$), focusing on their stability with respect to variations in temperature and process parameters, in the context of integrated micropower management circuits. The first technique combines Proportional-to-Absolute-Temperature (PTAT) and Complementary-to-AbsoluteTemperature (CTAT) currents generated with the support of operational amplifiers, to generate the ($V_{R E F}$). The second technique utilizes a self-biased current mirror for generating a PTAT current, while the CTAT current is again generated with the previously used opamp-based circuit, and both currents are added to generate the $V_{R E F}$. A band-gap reference (BGR) design involves a bandgap core, a summing circuit, and a start-up circuit to apply the correct bias. Both BGR1 and BGR2 circuitry provides a voltage reference of 900 mV over $-40^{\circ} \mathrm{C}$ to $100^{\circ} \mathrm{C}$ temperature range with a power supply (VDD) of 1.2 V.