body diode of MOSFET

[senmeis]

Hi,

in motor drive circuit the so called body diode is always referred such as on page 3 of the document: https://training.ti.com/sites/default/files/docs/brushed_dc_motor_2-the_h-bridge.pdf. This diode is by no means a physical one.

My question is if it’s the same body diode found on page 3 of this document:
https://training.ti.com/sites/defau...slew-rate-settling-time-presentation-quiz.pdf
?

 

[wwfeldman]

one of these may help:

this seems most likley:

https://www.ixys.com/Documents/AppNotes/IXAN0061.pdf

Common misconceptions about the MOSFET body diode - Power Electronic Tips

www.powerelectronictips.com

What is the MOSFET body diode?

Unlike virtually every other active device, the power MOSFET is unusual in that its schematic symbol includes a parasitic device – the body diode. The body diode is intrinsic to the device’s structure.

www.powerelectronictips.com

 

[crutschow]

This diode is by no means a physical one.

It is not a separate physical diode, but it is certainly real.

 

[Easy peasy]

My question is if it’s the same body diode found on page 3 of this document:

Well - it's not the same diode - but - somewhat similar, the body diode or intrinsic diode in a mosfet is a by product of the easiest construction ( at is the inherent parasitic BJT ) - this is also true of the op-amp ( and many other IC's ) that have a substrate of typically N material, but can be P too ), and diffuse "wells" into it to form the parts of the IC - there's no free lunch in IC wafer fabrication

[ p.s. this inherent but normally reversed biased diode in the IC often causes "latch-up" issues if somehow the voltage on the substrate goes high enough relative to other pins for conduction to happen - in the old days the substrate connection was some times brought out to connect it to a low potential to ensure this never happened ].