Ken Ueno Tetsuya Hirose Tetsuya Asai Yoshihito Amemiya A 300 nW, 7 ppm/degreeC CMOS voltage reference circuit based on subthreshold MOSFETs. 95-96 2009 ASP-DAC http://doi.acm.org/10.1145/1509633.1509658 conf/aspdac/2009 db/conf/aspdac/aspdac2009.html#UenoHAA09