US3798468A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Analog voltage switch
Assignee: Texas Instruments Inc
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Filing: 1972-11-22
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Granted: 1974-03-19
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Expires: 1992-11-22
Abstract
Abstract This disclosure concerns an analog voltage switch in which the output thereof reproduces as exactly as possible the analog voltage supplied to the input. The analog voltage switch includes a plurality of channels, each of which is provided with an analog voltage input and a control input for enabling the channel to be selected. The selected channel as determined by the control input receives an analog voltage input which appears at the output thereof. The analog voltage switch employs primarily semiconductor components and is especially applicable to use in an integrated form in that current amplifications of complementary semiconductor components and forward voltages of diodes employed in the analog voltage switch are of substantially the same magnitude and constant current sources included therein supply substantially the same current. By virtue of this arrangement, the temperature-dependent deviations of the semiconductor components employed in the analog voltage switch effectively cancel out each other such that the circuit comprising the analog voltage switch is substantially independent of temperature.
Inventors
- 👤 K Elshuber
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 07:31
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/14; H03F; H03F3/00; H03F3/72; H03K17/51; H03K17/56; H03K17/60; H03K17/62; H03K17/6257
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
471 words
An analog voltage switch comprising: a plurality of channels, each of said channels having: an analog voltage input and a control input for selecting the channel; a pair of transistors of complementary conductivity types, each having a collector, base and emitter; a common connection between the emitter of one of said pair of transistors and the collector of the other one of said pair of transistors; the collector of said one transistor and the emitter of said other transistor connected to a first reference potential; a constant current source for said channel comprising a third transistor having a collector, base and emitter, the collector-emitter path of said third transistor connected in series between a second reference voltage and said common connection of said pair of transistors; first means including a first diode connecting said analog voltage input to the base of a normally nonconductive one of said pair of transistors, said first diode being poled in the same direction as the base-emitter junction of said normally non-conductive transistor; second means connecting said control input to the base of a normally conductive one of said pair of transistors, and a second diode connected to said common connection of said pair of transistors and poled in an opposite direction from that of the base-emitter junction of said normally non-conductive one of said pair of transistors; an output transistor connected to an analog voltage output common to all said channels and of complementary conductivity type with respect to that of the normally non-conductive transistor of each channel, said output transistor having a collector, base and emitter; the emitter-collector path of said output transistor connected to a second constant current source comprising a fourth transistor having a collector, base and emitter, the emitter-collector path of said fourth transistor connected in series with the emitter-collector path of said output transistor; means for applying a constant bias to the base of each of said third transistors and to the base of said fourth transistor; the normally-conductive transistor of each said pair of transistors of said channels being responsive to a respective control signal applied to the control input of a particular channel in selecting that channel by changing the conductive state of the normally nonconductive transistor of said selected channel to a conductive state thereby transmitting an analog voltage signal received at said analog voltage input of the selected channel substantially without loss to said analog voltage output; and wherein all of said transistors, diodes and resistors comprise circuit elements of an integrated circuit wherein any temperature drift of said first diode in each channel is substantially compensated by corresponding temperature drift of said second diode in that channel; and any temperature drift of each normally nonconductive transistor of said pair of transistors of each channel is substantially compensated by corresponding temperature drift of said output transistor.
Claim 2
Dependent Claim
471 words
An analog voltage switch comprising: a plurality of channels, each of said channels having: an analog voltage input and a control input for selecting the channel; a pair of transistors of complementary conductivity types, each having a collector, base and emitter; a common connection between the emitter of one of said pair of transistors and the collector of the other one of said pair of transistors; the collector of said one transistor and the emitter of said other transistor connected to a first reference potential; a constant current source for said channel comprising a third transistor having a collector, base and emitter, the collector-emitter path of said third transistor connected in series between a second reference voltage and said common connection of said pair of transistors; first means including a first diode connecting said analog voltage input to the base of a normally nonconductive one of said pair of transistors, said first diode being poled in the same direction as the base-emitter junction of said normally non-conductive transistor; second means connecting said control input to the base of a normally conductive one of said pair of transistors, and a second diode connected to said common connection of said pair of transistors and poled in an opposite direction from that of the base-emitter junction of said normally non-conductive one of said pair of transistors; an output transistor connected to an analog voltage output common to all said channels and of complementary conductivity type with respect to that of the normally non-conductive transistor of each channel, said output transistor having a collector, base and emitter; the emitter-collector path of said output transistor connected to a second constant current source comprising a fourth transistor having a collector, base and emitter, the emitter-collector path of said fourth transistor connected in series with the emitter-collector path of said output transistor; means for applying a constant bias to the base of each of said third transistors and to the base of said fourth transistor; the normally-conductive transistor of each said pair of transistors of said channels being responsive to a respective control signal applied to the control input of a particular channel in selecting that channel by changing the conductive state of the normally nonconductive transistor of said selected channel to a conductive state thereby transmitting an analog voltage signal received at said analog voltage input of the selected channel substantially without loss to said analog voltage output; and wherein all of said transistors, diodes and resistors comprise circuit elements of an integrated circuit wherein any temperature drift of said first diode in each channel is substantially compensated by corresponding temperature drift of said second diode in that channel; and any temperature drift of each normally nonconductive transistor of said pair of transistors of each channel is substantially compensated by corresponding temperature drift of said output transistor.
Claim 3
Dependent Claim
192 words
An analog voltage switch according to claim 1, wherein the said means for applying a constant bias to the base of each of said third transistors and to said fourth transistor comprises a first potential divider connected between said first and second reference potentials; said potential divider including a fifth transistor having a collector, base and emitter, the collector of said fifth transistor connected by a diode to said second reference potential, the emitter of said fifth transistor connected by a resistor to said first reference potential, and the base of said fifth transistor connected to a tap on a resistor-diode potential divider cOnnected between said first and second reference potentials; the collector of said fifth transistor further being connected to the base of each of said third transistors to apply said constant bias thereto; a sixth transistor having a collector, base and emitter, the emitter-collector path of said sixth transistor connected to said second reference potential and by a third diode to said first reference potential, a junction between said third diode and said sixth transistor being connected to the base of said fourth transistor to supply said constant bias thereto.
References Cited (Backward Citations)
US3526785A
Cited
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Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-03-18 | 1977-09-17 | 1978-03-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-18 | 1981-09-17 | 1982-03-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-18 | 1985-09-17 | 1986-03-19 | $7700.00 | Window Closed / Lapsed |