Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Patent
1979-03-30
1981-05-19
Salce, Patrick R.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
330143, 330298, 330207P, 361103, H02H 504, H03F 304
Patent
active
042688876
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 heat-sensitive monitoring transistor by way of a diode in bucking relationship with its base/emitter path, the monitoring transistor being part of a protective circuit which reduces the input signal to the power amplifier in the event of an overload. The monitoring transistor is separated from the power transistor, on the silicon chip of the amplifier, by a distance so chosen that an overload raising the temperature of the power amplifier will significantly reduce the operating threshold of the monitoring transistor only if the overload persists for a minimum period on the order of one millisecond. To minimize the dependency of the sensitivity of the protective circuit upon ambient temperature, the diode is also of heat-sensitive character and is positioned on the chip at a distance from the power transistor greater than that of the monitoring transistor so as to compensate in part for the lowering of its threshold in the case of longer-lasting temperature rises.
REFERENCES:
patent: 3258606 (1966-06-01), Meadows
patent: 3393328 (1968-07-01), Meadows et al.
patent: 3421102 (1969-01-01), Andrews
patent: 3440352 (1969-04-01), Boll
patent: 3792316 (1974-02-01), Bondini et al.
patent: 3809928 (1974-05-01), Evans
patent: 4074334 (1978-02-01), D'Arrigo et al.
patent: 4157513 (1979-06-01), Ghiringelli et al.
Ghiringelli Giovanni
Murari Bruno
Ross Karl F.
Salce Patrick R.
SGS-ATES Componenti Elettronici S.p.A.
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