Unfortunately (or fortunately), body diodes are physically part of the construction of power FETs because the body of the FET is directly connected to the source to avoid the unwanted turn on of a parasitic BJT.
Both the cap and diode are parasitic elements of power FETs. That being said, there are some situations where we actually do want both a cap and/or a diode in parallel with a FET and may place them there. Increasing the parallel cap can slow down the rate of change of voltage across the FET. Adding an additional anti parallel diode (maybe a zener) can reduce loss compared to periods where only the body diode is forced to conduct.
Hi Tim, do you provide design services, do you have a website or email address to contact you ? I am interested in designing 300-500 nanosecond pulses into resistive loads using transformers rather than capacitors .
Hi Tim ,thanks for such an intuitive lecture, may I know which books/ reference do you follow?
What is the use of that body diode across the FET? No use when turn on and off modes?
Unfortunately (or fortunately), body diodes are physically part of the construction of power FETs because the body of the FET is directly connected to the source to avoid the unwanted turn on of a parasitic BJT.
Why capacitors are placed across the FET and diode?
May be switches to protect from voltage stress?
Both the cap and diode are parasitic elements of power FETs. That being said, there are some situations where we actually do want both a cap and/or a diode in parallel with a FET and may place them there. Increasing the parallel cap can slow down the rate of change of voltage across the FET. Adding an additional anti parallel diode (maybe a zener) can reduce loss compared to periods where only the body diode is forced to conduct.
Hi Tim, do you provide design services, do you have a website or email address to contact you ? I am interested in designing 300-500 nanosecond pulses into resistive loads using transformers rather than capacitors .
You can send me an email at drtimmcrae@gmail.com