Encoding analog signal amplitudes into digitized form has become one of the fundamental operations in microelectronics integrated circuits. Hundreds of engineers and scientists have contributed to the development of this field. Recent surveys have studied the evolution of A/D chip performance over the past few years; these include a 2010 study by Jonsson  and Murmann's online spreadsheet covering the period 19972012 . It is naive to think that one could do justice to such a history here in only a few pages. Moreover, many authorative publications have already treated the electronic and practical details as well as the historical background. Examples include fairly recent books by Walt Kester of Analog Devices  and Marcel Pelgrom of NXP, formerly Philips ; a 1978 tutorial article by Bernard Gordon ; and a textbook on pulse code modulation by K. W. Cattermole . Gordon, who until recently was still active at Analogic Corp. and who in the 1950s pioneered analog-to-digital converters (ADCs) for avionics and missile telemetry, noted in his 1978 paper that the overall field of data conversion has sprung from two distinct fountainheads. [One was in the] late 1930s [with the invention of] coding and decoding for pulse code modulation, primarily for telephone communication. Not until the early 1950s [did the second arrive:] instrumentation-oriented data conversion. To a large extent the efforts from these two diverse sources have proceeded independently and with some resulting confusion in terminology .