How does a MOSFET get damaged?
If the maximum operating voltage of a MOSFET is exceeded, it goes into Avalanche breakdown. If the energy contained in the transient over-voltage is above the rated Avalanche energy level, then the MOSFET will fail. The device fails short circuit, initially, with no externally visible signs.
Why bulk is used in MOSFET?
The MOSFET is a device that has 4 terminals (gate, drain, source and bulk), in which a voltage at the gate controls the current that flows between the drain and source. The voltage in the bulk plays a minor role and is often not shown in the symbol.
What kind of voltage does a MOSFET need to fail?
For example, a suitably high voltage applied between the gate and source (VGS) will break down the MOSFET gate oxide. Gates rated at 12 V will likely succumb at about 15 V or so; gates having a 20-V rating typically fail at around 25 V.
Why does the MOSFET gate driver have any influence?
Does the MOSFET gate driver have any influence in the case of disturbances? Interferences occurring in the device or field can, for example, bring additional charge to the gate via the parasitic mill capacity (from drain to source). This can cause the switching transistor to switch on undesirably and cause a bang.
What happens when transistors overlap in a MOSFET?
Here, if the control signals to the MOSFETs overlap, the transistors will effectively short-circuit the supply. This is known as a shoot-through condition. When it arises, any supply decoupling capacitors discharge rapidly through both MOSFETs during every switching transition, causing short but large current pulses.
Why are fast recovery diodes used in MOSFET gate?
This ensures that the MOSFET body diode is never driven into conduction. The free-wheel current is handled by the fast recovery diodes which present less of a “shoot-through” problem. If the MOSFET gate is driven with too high a voltage, then the gate oxide insulation can be punctured rendering the device useless.