A mixed potential NOx sensor apparatus for measuring the total NOx concentration in a gas stream is disclosed. The NOx sensing apparatus comprises a multilayer ceramic structure with electrodes for sensing both oxygen and NOx gas concentrations and includes screen-printed metallized patterns that function to heat the ceramic sensing element to the proper temperature for optimum performance. This design may provide advantages over the existing technology by miniaturizing the sensing element to provide potentially faster sensor light off times and thereby reduce undesired exhaust gas emissions. By incorporating the heating source within the ceramic sensing structure, the time to reach the temperature of operation is shortened, and thermal gradients and stresses are minimized. These improvements may provide increased sensor performance, reliability, and lifetime.