A CMOS bandgap reference with an inaccuracy of ±0.15% (3 σ) from -40°C to 125°C is presented. In contrast to prior art, it requires only a single trim to achieve this level of precision. A detailed analysis of the various error sources is provided, and techniques to reduce them are discussed. The prototype bandgap reference draws 55 μA from a 1.8 V supply, and occupies 0.12 mm2 in a 0.16 μm CMOS process. Experimental results from two runs show that, with the use of chopping and higher-order curvature correction to remove non-PTAT errors, the residual error of a bandgap reference is mainly PTAT, and can be removed by a single room temperature trim.