Patent US4605866A successfully refreshed from Google Patents.
US4605866A
Expired / Lapsed
US
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D.C. biassing of MESFETs to prevent oscillation during power supply switching
Assignee: Nortel Networks Ltd
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Filing: 1984-04-11
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Granted: 1986-08-12
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Expires: 2004-04-11
Abstract
Abstract Current in the drain-source path of a microwave high-power GaAs MESFET is controlled by a regulating circuit including an integrating differential amplifier whose output controls the gate of the MESFET. One input of the differential amplifier is supplied with a fraction of the supply voltage, and the other is supplied with a voltage dependent upon the current to be controlled. During switch-on and switch-off of the supply voltage, the risk of Gunn effect oscillation of the MESFET is avoided by a switching circuit which controls the differential amplifier to maintain substantially zero drain-source current when the supply voltage is below a predetermined level less than its nominal level.
Inventors
- 👤 David R. Conn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 13:57
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/30; H03F1/305; H03F1/306
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
82 words
A d.c. biassing circuit for a MESFET having a gate and a controlled path including a drain and a source, comprising: means connected to the controlled path for deriving current therefor from a supply voltage: regulating means connected to the gate of the MESFET for controlling the gate to regulate the current in the controlled path; and switching means responsive to the supply voltage being below a predetermined level for controlling the regulating means to limit the current in the controlled path.
Claim 2
Dependent Claim
82 words
A d.c. biassing circuit for a MESFET having a gate and a controlled path including a drain and a source, comprising: means connected to the controlled path for deriving current therefor from a supply voltage: regulating means connected to the gate of the MESFET for controlling the gate to regulate the current in the controlled path; and switching means responsive to the supply voltage being below a predetermined level for controlling the regulating means to limit the current in the controlled path.
Claim 3
Dependent Claim
27 words
A circuit as claimed in claim 1 wherein the means for deriving current comprises a resistor connected in series between the controlled path and the supply voltage.
Claim 4
Dependent Claim
37 words
A circuit as claimed in claim 2 wherein the regulating means comprises amplifier means responsive to the current in the controlled path flowing through said resistor to control the gate of the MESFET to regulate the current.
Claim 5
Dependent Claim
75 words
A circuit as claimed in claim 2 wherein the regulating means comprises: means for producing a first potential from the supply voltage; means for producing a second potential from the supply voltage minus the voltage dropped across said resistor by the current in the controlled path flowing through said resistor; and differential amplifier means responsive to the first and second potentials for controlling the gate of the MESFET in response to differences between said potentials.
Claim 6
Dependent Claim
20 words
A circuit as claimed in claim 4 wherein the means for producing the first and second potentials comprise voltage dividers.
Claim 7
Dependent Claim
15 words
A circuit as claimed in claim 4 wherein the differential amplifier means comprises an integrator.
Claim 8
Dependent Claim
89 words
A circuit as claimed in claim 4 wherein the switching means comprises: a transistor stage having an output coupled to an input of the differential amplifier means; and means for causing said transistor stage to conduct current when the supply voltage is below said predetermined level thereby to cause the differential amplifier means to control the gate of the MESFET to reduce the current in the controlled path to substantially zero, said means causing said transistor stage to be non-conductive when the supply voltage is above said predetermined level.
Claim 9
Dependent Claim
63 words
A circuit as claimed in claim 7 wherein the means for causing said transistor stage to be conductive or non-conductive comprises a further transistor stage coupled to the first-mentioned transistor stage, and potential divider means including a Zener diode for biassing the further transistor stage to conduct or not conduct current when the supply voltage is respectively above or below the predetermined level.
Claim 10
Dependent Claim
38 words
A circuit as claimed in claim 7 wherein the output of the transistor stage is coupled to the input of the differential amplifier means via a diode poled to be forward biassed when the transistor stage conducts current.
Claim 11
Independent Claim
68 words
A method of preventing oscillation of a high frequency MESFET during switch-on and switch-off of power to the MESFET, comprising the steps of: determining when a supply voltage, from which current in a controlled path of the MESFET is derived, is below a predeterminied level less than its nominal level; and, in response to such determination, controlling the MESFET to maintain substantially zero current in the controlled path.
Claim 12
Independent Claim
68 words
A method of preventing oscillation of a high frequency MESFET during switch-on and switch-off of power to the MESFET, comprising the steps of: determining when a supply voltage, from which current in a controlled path of the MESFET is derived, is below a predeterminied level less than its nominal level; and, in response to such determination, controlling the MESFET to maintain substantially zero current in the controlled path.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-08-11 | 1990-02-10 | 1990-08-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-08-11 | 1994-02-10 | 1994-08-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-08-11 | 1998-02-10 | 1998-08-12 | $7700.00 | Window Closed / Lapsed |