Abstract: An apparatus and method of calibrating a signal sourcing device having a plurality of signal sources to reduce errors between signals generated by the signal sources by categorizing the signal sources into groups based on the amount of error in the signal generated by the signal sources and selecting the signal sources from the groups in a manner which reduces the overall error in selecting signals. For example, the signal sourcing device may be a digital to analog converter having a plurality of current sources that output currents which may have an error. Such an improved digital to analog converter would categorize the current sources into groups based on the amount of error in the current generated by the current sources and selecting the current sources from the groups in a manner which reduces the overall error in selecting signals for the conversion process. The groups may include a center group that straddles the median current generated by the current sources.