Patent US3789389A successfully refreshed from Google Patents.
US3789389A
Expired / Lapsed
US
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Method and circuit for combining digital and analog signals
Assignee: Westinghouse Electric Corp
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Filing: 1972-07-31
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Granted: 1974-01-29
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Expires: 1992-07-31
Abstract
Abstract A method and circuit for varying the amplitude of an analog signal in response to a digital signal particularly suited for use in subranged analog to digital converters. The analog signal is applied to one of two junctions interconnected by an impedance such as a resistor and an output signal is taken from the other of the two junctions. A constant current from one or more sources is selectively switched from one of the junctions to the other in response to the digital signal to thereby modify the amplitude of the analog signal by a discrete amount. The total current flow at the junction to which the analog signal is applied and attributable to the constant current source remains essentially constant irrespective of switching thereby minimizing the effects of switching transients. When utilized in connection with a subranged analog to digital converter, the invention eliminates the need for a differential amplifier or other subtracting circuit.
Inventors
- 👤 J Lenhoff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 23:05
CPC Classifications
H; H03; H03M; H03M1/00; H03M1/06; H03M1/08
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
158 words
A method for producing a first voltage having a known relationship to a second voltage, said relationship being determined by a digital signal, comprising the steps of: a. coupling an impedance between first and second junctions; b. applying said second voltage to said first junction to produce said first voltage at said second junction; and, c. selectively switching current from a source of essentially constant current from one of the junctions to the other junction in response to said digital signal to thereby vary the amplitude of said first voltage from one discrete voltage level to another, the switching being accomplished by decreasing the current from the current source to one of the junctions while substantially simultaneously increasing the current from the current source to the other junctioN so that the total current flow attributable to the constant current source at said first junction remains essentially constant thereby minimizing the effects of switching transients at the first junction.
Claim 2
Independent Claim
158 words
A method for producing a first voltage having a known relationship to a second voltage, said relationship being determined by a digital signal, comprising the steps of: a. coupling an impedance between first and second junctions; b. applying said second voltage to said first junction to produce said first voltage at said second junction; and, c. selectively switching current from a source of essentially constant current from one of the junctions to the other junction in response to said digital signal to thereby vary the amplitude of said first voltage from one discrete voltage level to another, the switching being accomplished by decreasing the current from the current source to one of the junctions while substantially simultaneously increasing the current from the current source to the other junctioN so that the total current flow attributable to the constant current source at said first junction remains essentially constant thereby minimizing the effects of switching transients at the first junction.
Claim 3
Dependent Claim
38 words
The method of claim 1 wherein the value of the change in voltage level of said first voltage signal is substantially equal to the product of the value of the switched current and the value of the impedance.
Claim 4
Independent Claim
127 words
The method for combining an analog signal with a digital signal comprising the steps of: a. providing a plurality of constant current sources each having a value weighted in accordance with the digital weight of a corresponding digit of the digital signal. b. providing two summing junctions interconnected by an impedance element; c. applying the analog signal to one of the two summing junctions; d. deriving an output voltage from the other of the two summing junctions; and, e. selectively switching the currents from the current sources from one of the summing junctions to the other of the summing junctions in response to the digital signal to thereby vary the output signal in amplitude as a function of both of the analog signal and the digital signal.
Claim 5
Independent Claim
127 words
The method for combining an analog signal with a digital signal comprising the steps of: a. providing a plurality of constant current sources each having a value weighted in accordance with the digital weight of a corresponding digit of the digital signal. b. providing two summing junctions interconnected by an impedance element; c. applying the analog signal to one of the two summing junctions; d. deriving an output voltage from the other of the two summing junctions; and, e. selectively switching the currents from the current sources from one of the summing junctions to the other of the summing junctions in response to the digital signal to thereby vary the output signal in amplitude as a function of both of the analog signal and the digital signal.
Claim 6
Independent Claim
119 words
The method for combining an analog signal with a digital signal comprising the steps of: a. providing a plurality of constant current sources; b. providing two summing junctions interconnected by impedance elements weighted in accordance with the digital weight of a digit of the digital signal; c. applying the analog signal to one of the two summing junctions; d. deriving an output voltage from the other of the two summing junctions; and, e. selectively and individually switching the current from current sources from one of the summing junctions to the other of the summing junctions in response to the digital signal to thereby provide an output signal related in amplitude to both the analog signal and the digital signal.
Claim 7
Independent Claim
119 words
The method for combining an analog signal with a digital signal comprising the steps of: a. providing a plurality of constant current sources; b. providing two summing junctions interconnected by impedance elements weighted in accordance with the digital weight of a digit of the digital signal; c. applying the analog signal to one of the two summing junctions; d. deriving an output voltage from the other of the two summing junctions; and, e. selectively and individually switching the current from current sources from one of the summing junctions to the other of the summing junctions in response to the digital signal to thereby provide an output signal related in amplitude to both the analog signal and the digital signal.
Claim 8
Dependent Claim
98 words
A circuit for modifying the amplitude of an analog signal from one discrete voltage level to another while minimizing the effects of switching transients comprising: impedance means operatively connected between first and second junctions circuit means for applying the analog signal to the first junction; a source of essentially constant current; and switching means for selectively switching current from said constant current source from one of the junctions to the other junction in response to a digital signal to thereby vary the amplitude of the analog signal at the second junction from one discrete voltage level to another.
Claim 9
Dependent Claim
98 words
A circuit for modifying the amplitude of an analog signal from one discrete voltage level to another while minimizing the effects of switching transients comprising: impedance means operatively connected between first and second junctions circuit means for applying the analog signal to the first junction; a source of essentially constant current; and switching means for selectively switching current from said constant current source from one of the junctions to the other junction in response to a digital signal to thereby vary the amplitude of the analog signal at the second junction from one discrete voltage level to another.
Claim 10
Dependent Claim
48 words
The circuit of claim 5 wherein said switching means comprises first and second transistors each connected to said current source and to a respective one of the first and second junctions, the digital signal controlling the switching of said switching means including a binary bit and its complement.
Claim 11
Dependent Claim
29 words
The circuit of claim 6 including isolation amplifier means operatively connected to said first junction, the analog signal being applied to said first junction through said isolation amplifier means.
Claim 12
Dependent Claim
78 words
A circuit for combining an analog voltage with a digital signal comprising: first and second junctions interconnected by resistor means; a plurality of sources of substantially constant current; circuit means for applying the analog voltage to the first junction; circuit means for providing an output signal from said second junction; and, means for applying current from said constant current sources selectively to one or the other of said first and second junctions in response to the digital signal.
Claim 13
Dependent Claim
78 words
A circuit for combining an analog voltage with a digital signal comprising: first and second junctions interconnected by resistor means; a plurality of sources of substantially constant current; circuit means for applying the analog voltage to the first junction; circuit means for providing an output signal from said second junction; and, means for applying current from said constant current sources selectively to one or the other of said first and second junctions in response to the digital signal.
Claim 14
Dependent Claim
37 words
The circuit of claim 8 including an analog to digital converter for generating the digital signal in response to the analog voltage, the digital signal representing at least a portion of the amplitude of the analog voltage.
Claim 15
Dependent Claim
58 words
The circuit of claim 9 wherein each of said means for applying current comprises first and second electronic switching meAns connected between said first and second junctions, respectively, and an associated one of said current sources, the operation of said first and second electronic switching means being mutually exclusive in response to appropriate bits of the digital signal.
Claim 16
Dependent Claim
45 words
The circuit of claim 10 wherein the values of said current sources are weighted in accordance with the digital weight of a corresponding digit in a predetermined digital code, each current source being switched in response to an equally weighted bit of the digital signal.
Claim 17
Dependent Claim
31 words
The circuit of claim 10 wherein said resistor means comprises a plurality of resistors weighted in value in accordance with the digital weight of corresponding digits of a predetermined digital code.
References Cited (Backward Citations)
US3311910A
Cited
US3573798A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-01-28 | 1977-07-30 | 1978-01-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-28 | 1981-07-30 | 1982-01-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-28 | 1985-07-30 | 1986-01-29 | $7700.00 | Window Closed / Lapsed |