Metrics were created to provide engineers a normalized method for comparing the energy consumed to the function performed. In most cases this yields a fraction with the energy consumed in the numerator and the function performed in the denominator. There are select metrics for each family of functions. For instance, operational amplifiers are actually divided into smaller groups such as precision, high speed, etc. This allows the metrics to focus on the performance level of the device family and provide the most accurate metric for comparison with other devices.