Method and apparatus for conversion of signal information between analog and digital forms

Signal information is converted between analog and digital form in a two-step process employing conversion apparatus having stable, but not necessarily highly accurate components. The component tolerances on such conversion apparatus are much greater than those on such conversion apparatus are much greater than those normally allowed on conventional conversion apparatus of equal accuracy. In an A/D conversion, an analog signal is first converted into an (n+m)-bit digital word in a special purpose digital code unique to the specific A/D conversion apparatus. The (n+m)-bit word is then translated into an n-bit word in binary digital code in accordance with a predetermined relationship therebetween. In a D/A conversion, an n-bit digital word in a binary digital code is first translated into a corresponding (n+m)-bit digital word in the special purpose digital code. The (n+m)-bit word is then converted into an equivalent analog signal; the latter step being performed by a conversion apparatus unique to the special purpose digital code. A plurality of A/D and D/A converters suitable for use with the present invention are disclosed. A number of converter calibration techniques are also disclosed.