“…Various VRs capable of operating with nano-watt (nW) power, or less, have been investigated [7]- [13]. The reference voltages of these VRs are based on the bandgap voltage of silicon (π BGR ) [7], [8], threshold voltage (π TH ) of a MOS-FET [9], [10], and threshold voltage difference (Ξπ TH ) [11]- [14]. However, almost all of them are realized in a singleended configuration, so differential or programmable VRs β The author is with the Division of Electrical, Electronic and Infocommunications Engineering, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka, 565-0871, Japan.…”