Abstract
Reference circuits have been studying for many years. Following the vigorous development of portable electronic products, integrated circuits with low voltage and small area have become the core part of the recent research. The bandgap reference circuits base on BJT and MOS for temperature compensation in recent years. The reference voltage is designed a low sensitivity voltage for temperature and supply voltage. However, the problem that resistances parallelizing on either side of BJT or MOS generally occupy quite large ratio of chip area under the consideration of power consumption and loading parasitic capacitances of op-amp still exist. The reference circuit is influenced by process variation. It is induced error voltage by process variation on reference voltage. The magnitude of the error voltage will influence the back-end of circuits on work. This thesis aims to improve the above problems and proposes a novel voltage reference circuit. A way of prediction on process mismatch will be presented. We design the first order and second order temperature compensation bandgap voltage reference circuits. Their temperature compensation based on current mirror to reduce the chip area and have a low offset voltage on op-amp. We used the error source to analyze the magnitude of reference voltage variation on BJT, resistances and current mirror mismatch. Besides, it has been implemented by a 0.18μm CMOS process. The measurable results of the first order temperature compensation circuits shows that the temperature coefficient is 215 ppm/℃ and produce a output reference voltage 446mV under the temperature range from 25 to 125 ℃ on the minimum supply voltage 1.2V. The chip area is 0.023 mm2. The measurable results of the second order temperature compensation circuit shows that the variation of temperature coefficient is 62 ppm/℃ under the temperature range from 25 to 125 ℃ and a supply voltage variation from 1 to 2V. The chip area is 0.06 mm2.