Accurate low power bandgap voltage

caroline11

The voltage of a bandgap reference is based on the bandgap voltage V,,, of a semiconductor: a well defined, temperature independent, physical value. In submicron CMOS digital processes, the lack of lateral pnps can be seen as a disadvantage. Without these components, we must rely on the well-known solution for a bandgap reference as shown in Fig. la, which requires the use of an opamp. In bipolar technologies, simple solutions for voltage references have been considered [l, 21. For CMOS processes the large offset of the opamp will reduce the accuracy of the output voltage 6. TO achieve better accuracy, laser trimming is a well-known solution although an expensive one. At low currents, the offset increases, and the challenge would be the realisation of a low power and accurate bandgap voltage reference in CMOS without laser trimming techniques. Furthermore, the available area is limited, so obtaining better resistor matching by increasing the area is not an option.