Other key ADC parameters are offset error and converter gain error. The offset error, often called the ‘zero-scale’ error, shifts the entire actual transfer function either up or down compared to the ideal transfer function as shown in graph on the bottom left. The red line represents the ideal ADC output and the blue line represents the actual output code of the ADC. Gain error changes the slope of the transfer function or compares the actual transfer function’s slope with the ideal transfer function as shown in the graph on the bottom right. Gain error is usually expressed in LSB or as a percent of full-scale range (%FSR), and it can be calibrated out with hardware or in software.