An offset compensation technique for bandgap voltage reference in CMOS technology

A precision integrated bandgap voltage reference in 0.35 mum CMOS technology is here presented. The circuit uses natural npn bipolar transistors as reference diodes. A particular attention was paid to the compensation of the several offsets that could strongly influence the performances of the reference. A very simple sample and hold technique for offset compensation is here presented. The proposed technique is straight forward for all bandgap topologies which use diodes with a terminal connected to the ground node or to the supply node. The temperature coefficient (TC) of the generated output voltage is 12.7 ppm/degC versus about 245 ppm/degC of the same circuit without offset compensation. A full description and an analytical expression for the proposed compensation technique are given. The results of the most relevant simulations are also reported. The circuit has been inserted in a test chip whose layout is shown.