Modern-day CMOS converters typically operate from 3.3- or 5-V power supplies. This will limit the on-chip voltage reference to a bandgap reference.
Reference technology in integrated circuits (ICs) is typically divided among three key product solutions: bandgap, buried Zener, and XFET references. This article will focus on the bandgap reference (BGR).
Bandgap Reference
Bandgap references need a high power-supply rejection ratio (PSRR), low quiescent current (Iq), low temperature coefficient (TC), and high accuracy. These references are composed of two transistors, each with different emitter areas that are used to generate a voltage proportional to absolute temperature.