A Bandgap Voltage Reference With Only MOS Transistors

The bandgap voltage reference (BGR) circuit is an important component of Analog-to-Digital and Digital-toAnalog converters, which are broadly used in mixed-signal and radio-frequency systems. Most BGR use bipolar junction transistors (BJT) to easily reduce the temperature dependence, due to temperature coefficients, other common practice is the use of operational amplifiers (OP-AMP). The goal is to implement a BGR architecture without the use of an op-amp and using only one type of transistors, in this case, CMOS technology, and without the use of parasitic BJT. This must be accomplished without compromising the specified voltage variation requirements, BGR with 1% variation. An all CMOS BGR without BJT and without Op-Amp is proposed and simulated using Xfab 0.18-μm process. The bandgap works with 1.8-V supply voltage with ±10% variation. The circuit generates an output reference voltage of 605.865 mV with a variation of ±3.325 mV over a temperature range from -40 to 85oC, which corresponds to 1.097% variation.