Abstract — This paper describes the design of a precision on-chip bandgap voltage reference for applications with CMOS analog circuits. Thecircuit uses naturally occurring vertical n-p-n bipolar transistors as reference diodes. P-tub diffusions are nsed as temperature-dependent resistorsto provide current bias, and an op-amp is used for voltage gain. The circuitis simple. Only two reference diodes, three p-tub resistors, and one op-ampare necessary to produce a reference with fixed voltage of – 1.3 V. An
additional op-amp with two p-tnb resistors will adjust the output to any desired value