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The body diode effect can be simulated in spice?

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chang830

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Hi,
we know, for the MOS transistor, there is a parasitic bipolar transistor or body diode when the its body and source shorted together. I wonder if this parasitic bjt or diiode can be simulated in spice simulation?

I asked this questiion is because our circuit will trigger this parasitic diode sometimes. I hope to evaualte its affect.

Thanks
 

MOS models contain the parasitic diode,
if you extract the layout it will use the parasitics, as well....
 

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    chang830

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Yes! if Vbs>about 0.7v, you can see big current!
just try it!
 

    C

    chang830

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butterfish said:
Yes! if Vbs>about 0.7v, you can see big current!
just try it!
Click to expand...

Hi butterfish,
I guess you mean Vsd>~0.7V or Vbd>~0.7V, it is not Vbs>~0.7V.Here, the source and body shorted. Right?
 

If you are worring about turning on the parasitic on the NMOS used a guard ring around it and tie it to the higher supply you have. Recommended reference "The Art of Analog Layout" by Alan Hasting.
 

chang830 said:
butterfish said:
Yes! if Vbs>about 0.7v, you can see big current!
just try it!
Click to expand...

Hi butterfish,
I guess you mean Vsd>~0.7V or Vbd>~0.7V, it is not Vbs>~0.7V.Here, the source and body shorted. Right?
Click to expand...

Yes, Vbs Vbd are same. as I know, in CMOS tech, if the parasitic diode maybe triged, you'd better care about latch-up problem. guard-ring should around it.
 

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