Systematic characterization of subthreshold- mosfets-based voltage references for ultra low power low voltage applications

For low power low voltage, low area applications, voltage references based on MOS transistors operating in subthreshold offer some attractive advantages over conventional bandgap-based structures. The lack of closed-form explicit expressions for the relationship between output and temperature for most subthreshold-based references makes it difficult to optimize performance and make quantitative comparisons with the performance of standard bandgap circuits. In this paper, a systematic and explicit characterization of the temperature characteristics for some of the basic subthreshold-based voltage references is presented. A quantitive comparison of the performance of the basic sub-threshold references with that of the basic bandgap references is presented which shows that the temperature coefficient of the two structures are comparable. It is shown that the explicit characterization of the subthreshold-based references is useful for assessing the performance potential of these structures.