Trimless second order curvature compensated bandgap reference using diffusion resistor

A trim-less second order curvature compensated bandgap reference current using diffusion resistor is presented. An order of magnitude higher sheet-resistance (x50) and tighter process control of diffusion resistor than the poly has enabled this work to achieve the same current in one-third area. The process spread of diffusion resistor and VPNP transistor tracks each other, thereby resulting in higher accuracy without using any trim techniques. The proposed circuit is fabricated in a 0.5 mum CMOS process. The measured reference current has a variation of 46 ppm/degC over a temperature range of -55degC to 125degC.