A fully CMOS low voltage bandgap reference without resistors

A new method to generate a reference voltage is introduced. A fraction of the forward voltage of a pn-junction implemented by a PMOS transistor with negative temperature coefficient (TC) is combined with a voltage produced by a CMOS floating proportional to absolute temperature (PTAT) voltage source. The combined output voltage will be a reference voltage with minimum variation with temperature while no resistance has been used in the circuit. The circuit is designed and simulated in a 0.18 μm CMOS technology which simulation results show the circuit is able to generate an output voltage of 695.6 mV with TC of 18 ppm/°C in the temperature range of −20°C to +120°C. Monte Carlo analysis considering both mismatch and process variations gives σ/μ=1.08%. The total power consumption of the circuit is about 8.9 μW at the supply voltage of 1.5V.