Superposition: The Hidden DAC Linearity Error
A digital-to analog converter (DAC) translates digital signals to analog signals. For example, a 12-bit DAC takes a 12-bit binary number, called an input code, and converts it into one of 4,096 analog output voltages or currents. When the contribution to the output voltage or current of each individual bit is independent of any other, it means that the device exhibits no superposition error or that "superposition holds." For a DAC with little or no superposition error, the linearity error for any given code will relate to the linearity error at some different code. This allows you to determine the worst case linearity error, and the digital code where that error occurs, with a very simple test.