Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
61 words
A digital-to-analog converter comprising switches controlled by digital signals having different weights, characterised in that there are more switches (62-74) than digital signals (12, 16, 18) and by a logic network (22) responsive to the digital signals to render conductive a number of the switches corresponding to the combined weights of such of the digital signals as have a particular value.
Claim 2
Dependent Claim
61 words
A digital-to-analog converter comprising switches controlled by digital signals having different weights, characterised in that there are more switches (62-74) than digital signals (12, 16, 18) and by a logic network (22) responsive to the digital signals to render conductive a number of the switches corresponding to the combined weights of such of the digital signals as have a particular value.
Claim 3
Dependent Claim
32 words
A digital-to-analog converter according to claim 1, characterised in that the switches (60 - 74) are connected in parallel to pass a current proportional to the number of switches which are conductive.
Claim 4
Dependent Claim
72 words
A digital-to-analog converter according to claim 1 or 2, characterised in that the logic network (22) comprises groups of gates (32 - 36; 42 - 54), each group comprising gates forming AND and OR functions of a corresponding digital signal and output .signals from the group corresponding to the next lower significance digital signal, and the switches (62 -74) being controlled by the gates respectively (42 -54) of the most significant group.
Claim 5
Dependent Claim
48 words
A digital-to-analog converter according to claim 3, wherein the digital signals are binary signals, characterised in that each group (e.g. 32, 34, 36) consists of 2 n OR gates and 2 n - 1 AND gates where the weight of the corresponding digital signal is 2 n .
Claim 6
Dependent Claim
43 words
A digital-to-analog converter according to any of claims 1 to 4, characterised by a supplementary lowest significance input digital signal line 14, and AND logic (24, 30, 40) responsive to all digital signals (12, 14, 16, 18) to control a further switch (60).
Claim 7
Dependent Claim
18 words
A digital-to-analog converter according to any of claims 1 to 5, characterised in that the switches are transistors.
Claim 8
Dependent Claim
55 words
A digital-to-analog converter according to claim 6, characterised in that the logic network (22) has outputs connected to gates or bases of the transistors (62 -74), sources or emitters of the transistors are connected to an output line (78) and drains or collectors of the transistors are connected to a voltage source (76 or 112).
Claim 9
Dependent Claim
50 words
A digital-to-analog converter according to claim 7, characterised in that every change of the combination of digital signals (12, 16, 18) having the said particular value representing an increase of the digital value to be converted causes exclusively the addition of a further conductive one of the switches (62 -74).
Claim 10
Dependent Claim
31 words
A digital-to-analog converter according to any of claims 1 to 8, characterised in that the switches (62 -74) and the logical network (22) are forned on an integrated circuit chip (80).
Claim 11
Dependent Claim
24 words
A digital-to-analog converter according to claim 9, characterised in that the switches which are conductive for each digital signal are distributed throughout the chip.
Claim 12
Dependent Claim
48 words
A digital-io-analog converter according to claim 9 or 10, characterised in that the chip (90) carries a plurality of modules (92, 94, 96, 98), each constituting a converter as defined in claim 1, the modules being usable together to extend the number of digits handled by the converter.
Claim 13
Dependent Claim
30 words
A digital-to-analog converter according to claim 11, characterised by further gates (102, 104) responsive to two signal lines (12, 106) to provide least-significant digit inputs to two modules (92, 94).
Claim 14
Dependent Claim
55 words
A digital-to-analog converter according to claims 1 to 12, characterised by a plurality of additional switches (110) acting as reference switches, means (114) for comparing the current passed by the reference switches with a reference current (116) and for adjusting (118) the voltage of a source (112) connected to the first said and additional switches.
Claim 15
Dependent Claim
70 words
14 . An analog-to-digital converter comprising a digital-to- analog converter (200) according to any of claims 1 to 13, characterised by means (192) for comparing an input analog signal (190) with the signal (194) from the digital-to-analog converter (200) and means (198) responsive to a resultant difference signal (196) to adjust the digital signals which are provided on output lines (199) and to the inputs of the digital-to-analog converter (200).