Patent US3678408A successfully refreshed from Google Patents.
US3678408A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Transistor protective circuit
Assignee: Sony Corp
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Filing: 1970-12-08
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Granted: 1972-07-18
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Expires: 1990-12-08
Abstract
Abstract A protective circuit for a transistor which limits the maximum allowable collector power loss so as to prevent the transistor from being destroyed is disclosed. A second transistor is connected in circuit with the main transistor to control the power loss in the main transistor. In one embodiment the protective transistor has a linear response and in another embodiment the protective circuit has a different slope in different operating ranges.
Inventors
- 👤 Tadao Suzuki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 11:09
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/08; H03K17/082; H03K17/0826; H03F; H03F1/00; H03F1/52
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
231 words
A protective circuit for protecting a main transistor which receives an input signal on its base from an input terminal comprising: a unilateral current device; a second transistor connected with its emitter and collector in series with the unilateral current device between the base of the main transistor and an output terminal; three resistors connected in series between the collector and emitter of the main transistor and developing a voltage proportional to the voltage between the emitter and collector of the main transistor; the base of the second transistor connected to the junction point between the one of said three resistors connected to the collector of said main transistor and the second of said three resistors to receive a signal indicative of the voltage between the emitter and collector of the main transistor; a fourth resistor connected to the emitter of said second transistor and to the junction point between said second and third resistors so as to supply a voltage proportional to the collector current of the main transistor to the second transistor such that when the voltage between the collector and emitter of the main transistor is low the collector voltage versus current characteristic of the main transistor will have a relatively steep slope and when the collector voltage exceeds a predetermined value the collector voltage versus current characteristic of the main transistor will have a relatively gentle slope.
Claim 2
Dependent Claim
231 words
A protective circuit for protecting a main transistor which receives an input signal on its base from an input terminal comprising: a unilateral current device; a second transistor connected with its emitter and collector in series with the unilateral current device between the base of the main transistor and an output terminal; three resistors connected in series between the collector and emitter of the main transistor and developing a voltage proportional to the voltage between the emitter and collector of the main transistor; the base of the second transistor connected to the junction point between the one of said three resistors connected to the collector of said main transistor and the second of said three resistors to receive a signal indicative of the voltage between the emitter and collector of the main transistor; a fourth resistor connected to the emitter of said second transistor and to the junction point between said second and third resistors so as to supply a voltage proportional to the collector current of the main transistor to the second transistor such that when the voltage between the collector and emitter of the main transistor is low the collector voltage versus current characteristic of the main transistor will have a relatively steep slope and when the collector voltage exceeds a predetermined value the collector voltage versus current characteristic of the main transistor will have a relatively gentle slope.
Claim 3
Dependent Claim
23 words
A protective circuit according to claim 1 comprising a fifth resistor connected between the emitter of said second transistor and said output terminal.
Claim 4
Dependent Claim
143 words
A protective circuit according to claim 2 including a third transistor with its base connected to the emitter of said main transistor and its collector connected to the collector of said main transistor and a sixth resistor connected between the emitter of said third transistor and the junction point between said second and third resistors. 4 A protective circuit according to claim 3 including a fourth transistor of opposite type to said main transistor receiving said input signal on its base from said input terminal, seventh and eighth resistors connected in series between the emitter of said fourth transistor and said output terminal, a fifth transistor with its collector connected to said output terminal and its emitter connected to the base of said fourth transistor, and the base of said fifth transistor connected to the junction point between said seventh and eighth resistors.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-07-18 | 1976-01-17 | 1976-07-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-18 | 1980-01-17 | 1980-07-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-18 | 1984-01-17 | 1984-07-18 | $7700.00 | Window Closed / Lapsed |