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Secondary breakdown is a failure mode in bipolar power transistors. In a power transistor with a large junction area, under certain conditions of current and voltage, the current concentrates in a small spot of the base-emitter junction. This causes local heating, progressing into a short between collector and emitter.
One style of current limiting circuit is shown in the image. The schematic represents a simple protection mechanism used in regulated DC supplies and class-AB power amplifiers. Q1 is the pass or output transistor. R sens is the load current sensing device. Q2 is the protection transistor which turns on as soon as the voltage across R sens ...
Snapback is a mechanism in a bipolar transistor in which avalanche breakdown or impact ionization provides a sufficient base current to turn on the transistor. It is used intentionally in the design of certain ESD protection devices integrated onto semiconductor chips.
A resistor removed from a high voltage tube circuit shows damage from voltaic arcing on the resistive metal oxide layer. Resistors can fail open or short, alongside their value changing under environmental conditions and outside performance limits. Examples of resistor failures include: Manufacturing defects causing intermittent problems.
Leaded chip carriers have metal leads wrapped around the edge of the package, in the shape of a letter J. Leadless chip carriers have metal pads on the edges. Chip carrier packages may be made of ceramic or plastic and are usually secured to a printed circuit board by soldering, though sockets can be used for testing.
A different form of short-circuit testing is done to assess the mechanical strength of the transformer windings, and their ability to withstand the high forces produced if an energized transformer experiences a short-circuit fault. Currents during such events can be several times the normal rated current.
Generally this means that high current circuits such as on chip power regulators use metal–oxide–semiconductor field-effect transistors (MOSFETs) for efficient control, and 'sea of logic' use conventional CMOS structures, while those portions of specialized very high performance circuits such as ECL dividers and LNAs use bipolar devices.
Conditional short-circuit current is the value of the alternating current component of a prospective current, which a switch without integral short-circuit protection, but protected by a suitable short circuit protective device (SCPD) in series, can withstand for the operating time of the current under specified test conditions.