Transistor protection circuit
US4021701A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 8, 1975 |
| Grant date | May 3, 1977 |
| Priority date | — |
| Expiry date | Dec 8, 1995 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG05F1/573
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
The disclosed protection circuit which is suitable for providing protection of transistors included in integrated circuits such as regulators and power amplifiers, includes thermal shutdown, safe area and current control circuits. The current control portion includes a sense transistor connected substantially in parallel with the transistor to be protected. In monolithic integrated circuit applications, the sense transistor has an emitter area that is a predetermined ratio of the emitter area of the protected transistor. A "sense resistor" is connected to the sense transistor and develops a control signal which is proportional to the instantaneous current being conducted by the protected transistor. A threshold circuit is coupled between the sense resistor and the drive circuit for the protected transistor and responds to the magnitude of the control signal crossing a predetermined threshold to remove or reduce the drive to the protected transistor.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.