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EEVblog => Other Blogs => Topic started by: ElectroIrradiator on August 04, 2015, 02:04:33 pm

Title: To whom it may concern: N vs. P channel MOSFETs.
Post by: ElectroIrradiator on August 04, 2015, 02:04:33 pm: (Yes, I do believe this is in the right forum section. :D )

Please be adviced that usually you[1] cannot replace an N channel MOSFET with a P channel ditto without suffering some dire consequences. That is why the first replacement MOSFET instantly blew up when you applied power. You shorted out the battery through the body diode, and the current was only limited by the DC resistance of the transformer. ;D

Otherwise enjoyed the video as always. :popcorn:

[1] Message meant for a fairly narrow selection of 'you'.
Title: Re: To whom it may concern: N vs. P channel MOSFETs.
Post by: McBryce on August 04, 2015, 02:11:21 pm: That's a VERY narrow "you" indeed. Any chance of a link to the video? :)

McBryce.
Title: Re: To whom it may concern: N vs. P channel MOSFETs.
Post by: ElectroIrradiator on August 04, 2015, 02:13:02 pm: Apparently Shahriar (https://www.eevblog.com/forum/testgear/teardown-repair-analysis-of-a-rohde-schwarz-fsh3-3-0ghz-spectrum-analyzer/) and I were typing our respective posts at the same time. ;D

Edit: I spelled Mr. S' name incorrectly... :palm:
Title: Re: To whom it may concern: N vs. P channel MOSFETs.
Post by: McBryce on August 04, 2015, 02:20:07 pm: It wouldn't be a Shahriar video if nothing exploded or caught fire :)

McBryce.
Title: Re: To whom it may concern: N vs. P channel MOSFETs.
Post by: dadler on August 05, 2015, 02:19:26 am: I am supremely confident that Shahriar knows the difference between P and N channel mosfets, considering he has a Ph.d in EE and works at Bell Labs (engineering manager, designing microwave-frequency ASICs)--in the building where the transistor was invented.
Title: Re: To whom it may concern: N vs. P channel MOSFETs.
Post by: ElectroIrradiator on August 05, 2015, 07:55:33 am: Quote from: dadler on August 05, 2015, 02:19:26 am
I am supremely confident that Shahriar knows the difference between P and N channel mosfets, considering he has a Ph.d in EE and works at Bell Labs (engineering manager, designing microwave-frequency ASICs)--in the building where the transistor was invented.

I know about his background in general terms.

I am also supremely confident that we all make those :palm: mistakes from time to time.
Title: Re: To whom it may concern: N vs. P channel MOSFETs.
Post by: MagicSmoker on August 05, 2015, 10:53:35 pm: Quote from: ElectroIrradiator on August 05, 2015, 07:55:33 am
...I am also supremely confident that we all make those :palm: mistakes from time to time.

Yes, this. I am always impressed when someone with a stellar pedigree does something exceptional stupid but still owns up to it; conversely, I am totally unamused when some wet-behind-the-ears intern blames an incomplete datasheet or the like for his/her failure.
Title: Re: To whom it may concern: N vs. P channel MOSFETs.
Post by: dadler on August 06, 2015, 12:15:02 am: In this case though, Shahriar just showed the wrong datasheet in the video. The newly-toasted mosfet in question was indeed N channel and actually only rated for 400mA. Hence why the to-220 mosfet was getting super hot, as the dc converter circuit really pulls a lot of current.
Title: Re: To whom it may concern: N vs. P channel MOSFETs.
Post by: Hugoneus on August 21, 2015, 04:11:00 pm: I just saw this! :)

In this case I showed the wrong datasheet in the video. As I was searching for replacement parts I downloaded many datasheets in the process. I added a note to the video.

Indeed if a PMOS would be used, it would put the DC-DC converter in positive feedback and would surely destroy the device in question.