Patent US3646587A successfully refreshed from Google Patents.
US3646587A
Expired / Lapsed
US
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Digital-to-analog converter using field effect transistor switch resistors
Assignee: Raytheon Co
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Filing: 1969-12-16
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Granted: 1972-02-29
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Expires: 1989-12-16
Abstract
Abstract A plurality of field effect transistors having their sourcedrain paths connected in parallel are operated as switch resistors under the control of respective digital input bit signals. When biased to conduction with a gate voltage at a uniform first preselected level, each switch resistor provides in its source-drain path a resistance Rn 2(n 1)R, where R is a predetermined resistance and n is a positive integer identifying the switch resistor in question. When biased with a gate voltage at a uniform second preselected level, each switch resistor is nonconductive. A plurality of gating field effect transistors selectively apply to the respective switch resistor gate electrodes respective voltages at essentially either the first or the second aforementioned preselected level as determined by the respective digital input bit signals. Output circuitry including an operational amplifier provides an analog voltage representative of the net current flow through the switch resistor source-drain paths.
Inventors
- 👤 Everett L Shaffstall
- 👤 Carroll R Perkins
- 👤 James L Gundersen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 20:30
CPC Classifications
H; H03; H03M; H03M1/00; H03M1/12; H03M1/18
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
250 words
A digital-to-analog converter comprising: a plurality of field effect transistor switch resistors, each having a current path and a control electrode and providing a capacitance therebetween, the respective current paths of said switch resistors being connected in parallel; one of said switch resistors being conductive of current such that a resistance R is provided in its current path when a voltage at a first preselected level is applied to its control electrode; each other of said switch resistors being conductive of current such that a different resistance related to the said resistance R in accordance with a preselected mathematical relationship is provided in its current path when a voltage essentially at said first preselected level is applied to its control electrode; each said switch resistor being essentially nonconductive of current when a voltage essentially at a uniform second preselected level is applied to its control electrode; gating means responsive to digital input signals and a series of gating pulses and, upon receipt of a gating pulse, for selectively applying to the respective control electrodes of said switch resistors a voltage at essentially either said first or said second preselected level as determined by the digital input signals, each said capacitance being of a value to substantially maintain said first voltage level at the associated control electrode until receipt of the next gating pulse; and output means coupled to the current paths of said switch resistors for providing an analog signal representative of the net current flow through said current paths.
Claim 2
Dependent Claim
250 words
A digital-to-analog converter comprising: a plurality of field effect transistor switch resistors, each having a current path and a control electrode and providing a capacitance therebetween, the respective current paths of said switch resistors being connected in parallel; one of said switch resistors being conductive of current such that a resistance R is provided in its current path when a voltage at a first preselected level is applied to its control electrode; each other of said switch resistors being conductive of current such that a different resistance related to the said resistance R in accordance with a preselected mathematical relationship is provided in its current path when a voltage essentially at said first preselected level is applied to its control electrode; each said switch resistor being essentially nonconductive of current when a voltage essentially at a uniform second preselected level is applied to its control electrode; gating means responsive to digital input signals and a series of gating pulses and, upon receipt of a gating pulse, for selectively applying to the respective control electrodes of said switch resistors a voltage at essentially either said first or said second preselected level as determined by the digital input signals, each said capacitance being of a value to substantially maintain said first voltage level at the associated control electrode until receipt of the next gating pulse; and output means coupled to the current paths of said switch resistors for providing an analog signal representative of the net current flow through said current paths.
Claim 3
Dependent Claim
38 words
A digital-to-analog converter according to claim 1 where each of said other field effect transistor switch resistors has a channel width-to-length ratio inversely related to that of said one switch resistor in accordance with said preselected mathematical relationship.
Claim 4
Dependent Claim
222 words
A digital-to-analog converter comprising: a plurality of field effect transistor switch resistors, each having a current path and a control electrode and providing a capacitance therebetween, the respective current paths of said switch resistors being connected in parallel; each said switch resistor being conductive of current such that a resistance Rn 2(n 1)R is provided in its current path when a voltage essentially at a uniform first preselected level is applied to its control electrode, where R is a predetermined resistance and n is a positive integer identifying the switch resistor in question; each said switch resistor being essentially nonconductive of current when a voltage essentially at a uniform second preselected level is applied to its control electrode; gating means responsive to digital input signals and a series of gating pulses and, upon receipt of a gating pulse, for selectively applying to the respective control electrodes of said switch resistors a voltage at essentially either said first or said second preselected level as determined by the digital input signals, each said capacitance being of a value to substantially maintain said first voltage level at the associated control electrode until receipt of the next gating pulse; and output means coupled to the current paths of said switch resistors for providing an analog signal representative of the new current flow through said current paths.
Claim 5
Dependent Claim
222 words
A digital-to-analog converter comprising: a plurality of field effect transistor switch resistors, each having a current path and a control electrode and providing a capacitance therebetween, the respective current paths of said switch resistors being connected in parallel; each said switch resistor being conductive of current such that a resistance Rn 2(n 1)R is provided in its current path when a voltage essentially at a uniform first preselected level is applied to its control electrode, where R is a predetermined resistance and n is a positive integer identifying the switch resistor in question; each said switch resistor being essentially nonconductive of current when a voltage essentially at a uniform second preselected level is applied to its control electrode; gating means responsive to digital input signals and a series of gating pulses and, upon receipt of a gating pulse, for selectively applying to the respective control electrodes of said switch resistors a voltage at essentially either said first or said second preselected level as determined by the digital input signals, each said capacitance being of a value to substantially maintain said first voltage level at the associated control electrode until receipt of the next gating pulse; and output means coupled to the current paths of said switch resistors for providing an analog signal representative of the new current flow through said current paths.
Claim 6
Dependent Claim
44 words
A digital-to-analog converter according to claim 3 wherein each said field effect transistor switch resistor identified by an integer n greater than one has a channel width-to-length ratio essentially equal to 1/2 (n 1) that of the switch resistor identified by the integer one.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-02-28 | 1975-08-30 | 1976-02-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-02-28 | 1979-08-30 | 1980-02-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-02-28 | 1983-08-30 | 1984-02-29 | $7700.00 | Window Closed / Lapsed |