Analog-to-digital and digital-to-analog converters and methods of operation

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION I.
Introduction The present invention relates to non-binary analog-to-digital and digital-to-analog conversion devices and associated methods for converting an analog input signal into a corresponding digital output word, and vice versa, that is accurate relative to the actual value of the input signal and not relative to a predetermined full scale input value.
The invention will hereafter be explained by first describing a conventional single-amplifier circulation A/D converter.
This is followed by a description of a single-amplifier circulation A/D converter that has been modified in accordance with the present invention, to produce a digital output that is accurate relative to the actual analog input.
A description of a generic model of a serial-feedback A/D converter is also provided.
This is followed by a description of the corresponding D/A converter.
II.
A Conventional Binary A/D Converter FIG.
1 is a schematic of a conventional single-amplifier circulation binary A/D converter.
The A/D converter receives an analog input signal V.
sub.
A and converts it through a process of n repetitive cycles into an n-bit binary digital output word.
The conventional A/D converter is illustrated and described in H.
Schmid, A/D Converters, Part 1, Electronic Design 25, pp.
58-62, Dec.
5, 1968.
The A/D converter includes a voltage-controlled analog switch 12.
The switch 12 has an input terminal 14 which receives an analog input voltage V.
sub.
A, and an output terminal 16 that receives the signal on terminal 14 depending upon whether the switch is closed or open.
A control terminal 18 receives a control signal T.
sub.
1 that controls the opening and closing of switch 12.
The signal T.
sub.
1 is shown in FIG.
5 as a timing signal that is high during an initial clock period representing the first of repetitive conversion cycles, and low at all other times thereafter.
The switch 12 will be closed when T.
sub.
1 is high, and open when T.
sub.
1 is low