This paper presents a simple structure to extract VGO, the silicon bandgap voltage at zero Kelvin. Based on a traditional Kuijk structure, a third diode with a temperature constant current is used to extract the curvature term. A novel Gm cell-based voltage summer is proposed to perform the curvature correction. A single temperature trimming is implemented to trim out PTAT errors and calibrate the gain of the summer. The bandgap reference circuit is simulated in the UMC 65nm process. With the proposed trimming method, a temperature coefficient less than 10 ppm/°C from -40 °C to 125 °C can be achieved.