Protective system for power stage of monolithic circuitry
US4157513A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 20, 1977 |
| Grant date | Jun 5, 1979 |
| Priority date | — |
| Expiry date | Dec 20, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H5/044
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A power transistor in the final stage of an IC amplifier feeding a reactive load, such as a loudspeaker, has an emitter resistor connected across the input of a monitoring transistor by way of a diode, the monitoring transistor being part of a protective circuit which reduces the input signal to the power amplifier in the event of an overload. To retard the response of the protective circuit, for the purpose of preventing signal distortions in the event of brief power surges, the diode and the monitoring transistor are so disposed on the silicon chip of the amplifier that a thermal wave from the overheating power transistor will first strike the diode, thereby reducing its resistance to compensate for an increased voltage drop across the emitter resistor, and will reach the monitoring transistor with a certain delay; if the overload persists, the resulting increase in the conductivity of the monitoring transistor re-establishes the full sensitivity of the protective circuit.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.