What is meant by secondary breakdown in transistor?
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.
Which device is free from second breakdown?
Secondary breakdown can be avoided by using power transistor in safe operating area. The safe operating area (SOA) of a power transistor specifies the safe operating limit of collector current IC verses collector emitter voltage VCE.
What is transistor breakdown?
The Breakdown Region of a transistor is the region where the collector voltage, Vcc, is so large that the collector-base diode breaks down, causing a large, undesired collector current to flow. The breakdown region should always be avoided in transistor circuits. …
What is primary breakdown in power transistor?
The primary breakdown shown takes place because of avalanche breakdown of collector base junction. Large power dissipation normally leads to primary breakdown. The second breakdown shown is due to localized thermal runaway. 0.5V, the transistor than goes into saturation.
Why there is no secondary breakdown in MOSFET?
While current is flowing because of avalanche breakdown, the gate is off, and therefore no current flows through the gate channel. Consequently, the MOSFET is not susceptible to secondary breakdown because it is not affected by the temperature-dependency characteristics of the gate threshold voltage Vth.
What is meant by IGBT?
IGBT stands for insulated-gate bipolar transistor. It is a power transistor that combines an input MOS and an output bipolar transistor.
What do you mean by second breakdown?
Secondary breakdown is a failure mode in bipolar transistors in which negative resistance (current concentration) occurs under high-voltage and high-current conditions. Current concentration causes local heating, resulting in a small hotspot.
What are break down devices?
3 LEARNING OBJECTIVES What are Breakdown Devices ? These are solid-state devices whose working depends on the phenomenon of avalanche breakdown. They are sometimes referred to by the generic name of thyristor which is a semiconductor switch whose bistable action depends on P-N-P- N regenerative feedback.
What are the two types of breakdown in transistors?
The Avalanche Breakdown and Zener Breakdown are two different mechanisms by which a PN junction breaks. The Zener and Avalanche breakdown both occur in diode under reverse bias.
What is secondary breakdown in bipolar power transistors?
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.
What is the secondary breakdown in a BJT?
Secondary breakdown is basically a drawback of BJTs, particularly in power transistors. Ohm’s law states that voltage equals current times resistance, which shows that as resistance decreases, current increases at a constant voltage.
What is the breakdown voltage of a silicon transistor?
At voltages between 4Eg/q and 6Eg/q, the breakdown is a combination of the two effects. Since the energy band gap in silicon decreases with temperature, the breakdown voltage due to tunneling effect in these semiconductors has a negative temperature coefficient.
What causes a power transistor to be destroyed?
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. This often leads to the destruction of the transistor.