| Bandgap References, which are widely used in systems such as A/D and D/A converters, dynamic memory and flash memory, are of paramount importance in analog circuits, for its temperature stability and anti-noise properties affect precision and porformance of the entire system. However, the traditional circuit structure of bandgap reference can not meet the requirements of the development of modern integrated circuits.Based on a thorough research into the structure and characteristics of BGR, and a perceptive analysis of its non-ideal factors, a novel bandgap reference chip with fine temperature coefficients and low offset is designed and implemented by adopting an improved Kujik structure. Specifically, the main contents are provided below;a) Chopper modulation technique is used to eliminate input offset voltage and low frequency noise of operational amplifier. And with improved performance of the op amp, noise resisting ability of bandgap reference is also improved.b) Fast star-up circuit and bias circuit for BGR are well designed using supply-independent biasing techniques, which result in an improved PSRR and supply voltage regulation. Consequently, the bandgap reference has a good stability both in temperature and in supply voltage.c) Advanced layout techniques such as common centroid and interdigtaed is adopted, matching the current mirrors, the input pair of differential amplifier, PNP and so on.Based on above mentioned, HSPICE is finally used to make a full simulation for our bandgap reference chip. As the result, the bandgap reference is proved to be with a good performance as following:(1) temperature coefficients of 6ppm/℃in the range of-40℃～85℃;(2) output voltage of 1.26±0.002V as supply voltage changes between 2.7V to 5.5V;(3) typically 70dB PSRR;(4) only 70us start-up time. Consequently, the bandgap reference chip provided in this paper meets the design target for high performance performance, and provides a competitive advantage in the BGR market. |
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