US3566200A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Protective biasing circuit for transistors
Assignee: Individual
•
Filing: 1969-05-21
•
Granted: 1971-02-23
•
Expires: 1989-05-21
Abstract
Abstract A protective biasing circuit is described for transistors to control their leakage current and to provide reverse-polarity protection for them, this protective biasing circuit being particularly advantageous in use with power switching transistors of either the Germanium or Silicon types. The biasing circuit includes a transistor of the same polarity type and leakage characteristic as the transistor it controls and thermally coupled to the transistor it controls so that its temperature varies in the same manner as the one it controls. The emitters of the two transistors are connected together and the collector of the protective biasing transistor is connected to the base of the controlled transistor, and the base of the protective biasing transistor is connected through a resistor of relatively large resistance value in a predetermined range to a voltage point which is lower in potential than the source of the power for the controlled transistor.
Inventors
- 👤 Robert L Seidler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 09:18
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/08; H03K17/082; H03K17/0826
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
230 words
A protective biasing circuit for a controlled transistor for protecting the transistor against ''''thermal runaway'''' and also protecting it against the application of a reversed polarity current source, said protective biasing circuit comprising: a controlled transistor having an emitter electrode and a collector electrode of one polarity type and having a base electrode of the opposite polarity type; a power supply connection to said emitter electrode for supplying current thereto and an output connection from said collector electrode for feeding current controlled by said transistor to a load; a protective biasing transistor of the same polarity type and same leakage characteristics as said controlled transistor; thermal coupling means providing thermal coupling between said transistors for assuring that said biasing transistor remains at substantially the same temperature as said controlled transistor; said biasing transistor having its emitter electrode connected to the emitter electrode of said controlled transistor and having its collector electrode connected to the base electrode of said controlled transistor for placing the emitter-collector current flow path of said biasing transistor in parallel relationship with the emitter-base current flow path of sAid controlled transistor; said biasing transistor having its base connected to a resistor of relatively large resistance value; and the opposite side of said resistor being connected to a circuit connection point having a potential ''''less'''' than the supply potential applied to the emitter electrode of said controlled transistor.
Claim 2
Dependent Claim
230 words
A protective biasing circuit for a controlled transistor for protecting the transistor against ''''thermal runaway'''' and also protecting it against the application of a reversed polarity current source, said protective biasing circuit comprising: a controlled transistor having an emitter electrode and a collector electrode of one polarity type and having a base electrode of the opposite polarity type; a power supply connection to said emitter electrode for supplying current thereto and an output connection from said collector electrode for feeding current controlled by said transistor to a load; a protective biasing transistor of the same polarity type and same leakage characteristics as said controlled transistor; thermal coupling means providing thermal coupling between said transistors for assuring that said biasing transistor remains at substantially the same temperature as said controlled transistor; said biasing transistor having its emitter electrode connected to the emitter electrode of said controlled transistor and having its collector electrode connected to the base electrode of said controlled transistor for placing the emitter-collector current flow path of said biasing transistor in parallel relationship with the emitter-base current flow path of sAid controlled transistor; said biasing transistor having its base connected to a resistor of relatively large resistance value; and the opposite side of said resistor being connected to a circuit connection point having a potential ''''less'''' than the supply potential applied to the emitter electrode of said controlled transistor.
Claim 3
Dependent Claim
30 words
A protective biasing circuit for a controlled transistor as claimed in claim 1 in which said resistor has a resistance value in the range from 8,000 ohms to 80,000 ohms.
Claim 4
Dependent Claim
31 words
A protective biasing circuit for a controlled transistor as claimed in claim 2 in which said resistor has a resistance value within the preferred range from 10,000 ohms to 30,000 ohms.
Claim 5
Dependent Claim
50 words
A protective biasing circuit for a controlled transistor as claimed in claim 1 in which said connection point for the opposite side of said resistor is a voltage regulating circuit supplying a regulated voltage of potential ''''less'''' than the supply potential applied to said emitter electrode of said controlled transistor.
Claim 6
Dependent Claim
75 words
A protective biasing circuit for a controlled transistor as claimed in claim 1 in which the power supply has one side connected to the emitter of said controlled transistor and has the opposite side connected to a ''''ground'''' return circuit and in which said circuit connection point for the opposite side of said resistor having a potential ''''less'''' than the supply potential applied to the emitter of said controlled transistor is the ''''ground'''' return circuit.
Claim 7
Dependent Claim
50 words
A protective biasing circuit for a controlled transistor as claimed in claim 1 in which said circuit connection point for the opposite side of said resistor having a potential ''''less'''' than the supply potential applied to the emitter of said controlled transistor is the base electrode of said controlled transistor.
Claim 8
Dependent Claim
50 words
A protective biasing circuit for a controlled transistor as claimed in claim 1, in which said circuit connection point for the opposite side of said resistor having a potential ''''less'''' than the supply potential applied to the emitter of said controlled transistor is the collector electrode of said controlled transistor.
Claim 9
Dependent Claim
55 words
A protective biasing circuit for a controlled transistor as claimed in claim 1, in which said controlled transistor and said protective biasing transistor are both PNP type transistors; said thermal coupling means being a common heat sink of metal having good heat conduction characteristics; and said transistors being closely mounted on said common heat sink.
Claim 10
Dependent Claim
55 words
A protective biasing circuit for a controlled transistor as claimed in claim 1, in which said controlled transistor and said protective biasing transistor are both NPN type transistors; said thermal coupling means being a common heat sink of metal having good heat conduction characteristics; and said transistors being closely mounted on said common heat sink.
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) | 1974-02-22 | 1974-08-24 | 1975-02-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-02-22 | 1978-08-24 | 1979-02-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-02-22 | 1982-08-24 | 1983-02-23 | $7700.00 | Window Closed / Lapsed |