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Old 27th February 2006, 03:27 AM   #1
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Default Determining mosfet type

Determining mosfet type

Use the circuit bellow to determine mosfet type if you happen to not know of it

the circuit gives the mosfet a heat stress depending on bias and heatsink used
keep the test brief especially if you use a small or no heatsink this will also
depend on id current and vds of mosfet, dont use huge current that will heat up
the mosfet very quckly and keep the dissipation and temp of the mosfet within spec
use a low voltage ps 12-20v with medium current up to 2A depending on mosfet

if vds start decreasing 2-3v (switchoff ps) mosfet is vertical type

if vds start increases 2-3v (switchoff ps) mosfet is lateral type

cheers
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Old 27th February 2006, 03:47 AM   #2
lineup is offline lineup  Sweden
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Thanks very much, mastertech

I downloaded schematic to my audio folder.
Will become useful, if I ever get more into MOSFET designs.

thanks and regards
lineup
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Old 27th February 2006, 08:17 AM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
are all low power mosfets of the lateral type?

I ask because your method would identify To92 encased types.
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Old 28th February 2006, 02:24 AM   #4
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look AndrewT it can be used with any device

cant you see? what are you a novice

"I ask because your method would identify To92 encased types."

i see what you mean you are a novice

kind regards
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Old 28th February 2006, 02:35 AM   #5
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dude! that was a lil harsh!
Good schematic though! i have wondered about this on a few ocassions. **saves it also**
Thanks,
Owen
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Old 28th February 2006, 05:03 AM   #6
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What could be worse than being a novice?

I wonder...

...lots of human frailties to choose from...

...so many shortcomings are available just for the asking...

hmmm????
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Old 28th February 2006, 09:46 AM   #7
ilimzn is offline ilimzn  Croatia
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There are really very few lateral MOSFET types, most can be identified by other means, threshold voltage amongst them. The threshold voltage inflection point from positive to negative tempco occurs at about 100-200mA, so feeding a MOSFET with D connectd to G a constant 200mA current, and measuring D+G to S voltage (threshold) variation should be enough to determine what you are dealing with, if the threshold voltage magnitude itself, the case or the markings were not.
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Old 28th February 2006, 10:38 AM   #8
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George,

you're a fun guy, but sometimes you remind me of Donk in Crocodile Dundee.

Those who are familiar with Mosfets know how to differentiate a vertical from a lateral type. So your post is directed to the ones who are a novice related to Mosfets, not necessarily means they are retards.
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Old 28th February 2006, 03:59 PM   #9
AndrewT is offline AndrewT  Scotland
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Hi,
now that you have all had a go at winding each other up, can I ask my question again but rephrased?

Are all low power Mosfets of the lateral type?

If not, then it appears that Master's method would offer an alternative way of identifying them.

Certainly by the time you get to power Mosfets, they are available in both V & L types and Master's method has been shown to work.

& Yes, I will always be a novice and proud of the fact I am able to continue learning although somewhat slowly.
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Old 28th February 2006, 04:08 PM   #10
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Supporting Andrew's case a little more, yes I would like to know if TO92 cased devices are always lateral, as if they can be either vertical or lateral this test could be useful.

For MOSFETs in bigger cases this test is not necessary because all you need to do is check the pinout: GDS with D case is vertical, GSD with S case is lateral.
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