Abstract: Resistance temperature detectors (RTD) present second and third order non-linearities, and a linear signal processing circuit which converts the voltage on a Pt-100 RTD to an output voltage with 10 mV/^oC presents a maximum non-linearity error of 1.07 ^oC (10.7 mV) in the 0 to 85 ^oC temperature range. These non-linearities can be corrected digitally, but there are applications where a simple analog linearization can be used with advantages, as in the case of a direct interface of an RTD sensor with a 4-20 mA current loop transducer. The intrinsic curvature of the Brokaw bandgap voltage reference cell, caused by the non- linear variation of the bipolar transistor's VBE with temperature, can be used to create a compensation voltage that can be used to reduce the non-linearity of the signal processing circuit of resistance temperature. A discrete Brokaw bandgap reference cell using a bipolar analog array LM3046 and a high precision op-amp was designed, and the calculated values of the final circuit indicate that the non-linearity of the signal conditioning circuit of a Pt-100 RTD is reduced by one order of magnitude (down to approximately 0.14 ^oC) in the 0-85 ^oC temperature range.

Keywords: RTD, Bandgap curvature, Brokaw cell, Linearization, Temperature sensors.

.__________________________________________________________________________________________