An ultra-small capacitor-less LDO with controlled-resistance technique and MOSFET-only bandgap

In this paper, we propose an ultra-small low dropout regulator (LDO) for NFC tag combining two new techniques. Firstly, a voltage bandgap is designed using only MOSFET instead of BJT in conventional architecture to reduce significantly the chip size. Secondly, to increase the stability of LDO we proposed a controlled circuit to vary output resistance according to output-load current. The latter technique also allows removing the feedback capacitor normally used in a conventional LDO architecture. The proposed LDO has a stable output voltage at 1.8V with input voltage varying from 2.1V to 3.3 V, a maximum current of 10 mA, and only 0.0058 mm² chip area.