Patent US3681659A successfully refreshed from Google Patents.
US3681659A
Expired / Lapsed
US
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Amplifier protective circuit
Assignee: Sony Corp
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Filing: 1971-03-26
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Granted: 1972-08-01
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Expires: 1991-03-26
Abstract
Abstract A protective circuit for protecting transistor amplifiers in which the transistors are interconnected with certain impedances and diodes with switching elements such that voltages and currents applied to the transistor are detected and utilized to sense when a condition exists which would injure the transistor. Bridge circuits and diodes are interconnected with the transistor to be protected and in certain embodiments a switching transistor is used with the bridge circuit and diode to protect the transistor.
Inventors
- 👤 Tadao Suzuki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 09:29
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/52
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
198 words
An amplifier protective circuit comprising: a first transistor used for amplifying input signals supplied to a first electrode of the same; a voltage source; means for connecting a second electrode of said first transistor to said voltage source; first circuit means for connecting a third electrode of said first transistor to a load and detecting a voltage in proportion to a current flowing through said first transistor; second circuit means connected between the second and third electrodes of said first transistor; said second circuit means detecting a voltage proportional to a voltage between the second and third electrodes of said first transistor; a second transistor connected to the first electrode of said first transistor to limit the current flowing through said first transistor; a first electrode of said second transistor connected to said second circuit means so that said second transistor is operated by the detected outputs of said first and second circuit means; third circuit means connected between said second circuit means and ground; and, said third circuit means including at least one diode and varying the limiting conditions for current flow through said first transistor in response to the voltage detected by said second circuit means.
Claim 2
Dependent Claim
198 words
An amplifier protective circuit comprising: a first transistor used for amplifying input signals supplied to a first electrode of the same; a voltage source; means for connecting a second electrode of said first transistor to said voltage source; first circuit means for connecting a third electrode of said first transistor to a load and detecting a voltage in proportion to a current flowing through said first transistor; second circuit means connected between the second and third electrodes of said first transistor; said second circuit means detecting a voltage proportional to a voltage between the second and third electrodes of said first transistor; a second transistor connected to the first electrode of said first transistor to limit the current flowing through said first transistor; a first electrode of said second transistor connected to said second circuit means so that said second transistor is operated by the detected outputs of said first and second circuit means; third circuit means connected between said second circuit means and ground; and, said third circuit means including at least one diode and varying the limiting conditions for current flow through said first transistor in response to the voltage detected by said second circuit means.
Claim 3
Dependent Claim
29 words
An amplifier protective circuit as claimed in claim 1 wherein said first circuit means comprises a resistor connected between said third electrode of the first transistor and the load.
Claim 4
Dependent Claim
36 words
An amplifier protective circuit as claimed in claim 1 wherein said second circuit means comprises a plurality of series connected resistors and said third circuit means are connected to a junction point between said series-connected resistors.
Claim 5
Dependent Claim
30 words
An amplifier protective circuit as claimed in claim 3 wherein said first electrode of the second transistor is connected to one of the junction points between said series connected resistors.
Claim 6
Dependent Claim
22 words
An amplifier protective circuit as claimed in claim 1 wherein a third electrode of said second transistor is connected to the load.
Claim 7
Dependent Claim
27 words
An amplifier protective circuit as claimed in claim 1 wherein said third circuit means comprises a series-connected circuit including said one diode and at least one resistor.
Claim 8
Dependent Claim
36 words
An amplifier protective circuit as claimed in claim 1 wherein said first transistor is of the NPN type and said first, second and third electrodes of the first transistor are a base, collector and emitter, respectively.
Claim 9
Dependent Claim
40 words
An amplifier protective circuit in accordance with claim 1 further comprising fourth circuit means connected between said third circuit means and said load for supplying the third circuit means with a voltage proportional to the output voltage across the load.
Claim 10
Dependent Claim
56 words
An amplifier protective circuit as claimed in claim 8 wherein said third circuit means comprises a series-connected circuit of said one diode and at least one resistor, and said fourth circuit means supplies said diode with the voltage proportional to the output voltage across the load to vary the condition for switching operation of said diode.
Claim 11
Dependent Claim
49 words
An amplifier protective circuit as claimed in claim 9 wherein said fourth circuit means comprises a series-connected circuit of a second diode and a resistor, said second diode detecting the output voltage across the load and supplying the detected output to said one diode of said third circuit means.
Claim 12
Dependent Claim
158 words
A protective circuit comprising: an output transistor to which an input is supplied; a power supply connected to a first electrode of said output transistor; a first resistor with one side connected to a second electrode of said output transistor; a load connected to the other side of said first resistor; a protective transistor with a first electrode connected to the base electrode of said output transistor; second and fourth resistors connected in series between the base of said protective transistor and said one side of said first resistor; A diode connected between ground and the junction point between said second and fourth resistors; a third resistor connected in series with said diode between ground and the junction point between said second and fourth resistors; a fifth resistor connected between said power supply and the base of said protective transistor; and means for detecting the voltage across said load and coupling said detected voltage to said protective transistor.
Claim 13
Dependent Claim
158 words
A protective circuit comprising: an output transistor to which an input is supplied; a power supply connected to a first electrode of said output transistor; a first resistor with one side connected to a second electrode of said output transistor; a load connected to the other side of said first resistor; a protective transistor with a first electrode connected to the base electrode of said output transistor; second and fourth resistors connected in series between the base of said protective transistor and said one side of said first resistor; A diode connected between ground and the junction point between said second and fourth resistors; a third resistor connected in series with said diode between ground and the junction point between said second and fourth resistors; a fifth resistor connected between said power supply and the base of said protective transistor; and means for detecting the voltage across said load and coupling said detected voltage to said protective transistor.
Claim 14
Dependent Claim
14 words
A protective circuit according to claim 11 wherein said detecting means comprises a rectifier.
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) | 1975-08-01 | 1976-01-31 | 1976-08-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-08-01 | 1980-01-31 | 1980-08-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-08-01 | 1984-01-31 | 1984-08-01 | $7700.00 | Window Closed / Lapsed |