A precision voltage and current reference for the SNAP CCD readout IC

A bandgap reference circuit capable of generating precision voltages below the Vg0 of silicon has been fabricated in a 0.25um, 2.5 V CMOS process. The circuit described is based on an existing topology that intrinsically generates a temperature compensated reference current, which can then be mirrored to provide both current and voltage references. With regard to bandgap reference design, a major deficiency of most modern sub-micron CMOS processes is the lack of any well-characterized forward-biased junction device. A method of device measurement and parameter extraction is presented that allows for the precise simulation of a fixed diode layout for the temperature range -150 to +70 C. The extracted diode model was used to optimize the bandgap design. Measurements of the prototype IC indicate an initial accuracy of 35 mV, a PSRR >60 dB, 12-bit noise performance, and a 10 mV voltage deviation over a range of more than 150 C degrees.