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EP0074860A2
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Digital-to-analog converter
Assignee: Mindspeed Technologies LLC
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Filing: 1982-09-16
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Granted: —
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Expires: 2002-09-16
Abstract
Abstract A plurality of transistor switches (62 - 74) are connected in parallel between a voltage source (76) and an output line (78). There are more switches than input lines (12, 16 and 18) corresponding to three input bits with values 1, 2 and 4 respectively. A logical network (22) controls the switches so that every change of input bits representing an increase in the digital value exclusively adds a conductive transistor switch, whereby there are no discontinuities in the output analog current. The logical network (22) comprises groups of gates (32, 34, 36; 42 - 54) corresponding to each bit other than the least significant and each group forms AND and OR combinations from its own bit and the outputs of the preceding group. To enable modular expansion an additional least significant bit line (14) and gates (24,30,40) render an additional transistor switch (60) conductive when all bits have 1 value. The transistor switches and gates can all be combined in an integrated circuit chip, the switches corresponding to each bit being preferably distributed over the chip. Further distributed transistor switches pass a current which is compared with a reference to provide an error signal for controlling the voltage source (76).
Inventors
- 👤 Henry S. Katzenstein
- 👤 Herbert W. Sullivan
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 18:58
CPC Classifications
H; H03; H03M; H03M1/00; H03M1/12; H03M1/34; H03M1/38
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).
References Cited (Backward Citations)
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