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Old 12th Feb 2011, 9:04 pm   #1
Norm_N_Tam
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Default Which BF245 FET to use?

The reflex receiver circuit, link below, originally used a HEPF0015 FET which cross references to the BF245:

http://www.crystalradio.net/transist...ges/snare2.jpg


Now, BF245 FETs come in A, B and C versions and so I am wondering which version would be the best suited for this circuit?

Norman Bourassa
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Old 12th Feb 2011, 9:40 pm   #2
Sideband
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Default Re: Which BF245 FET to use?

It probably won't make a lot, if any, difference in that sort of circuit. Here is a data sheet that covers all three versions. You can compare it with the data sheet of the original type.


http://www.fairchildsemi.com/ds/BF/BF245C.pdf


SB
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Old 12th Feb 2011, 9:54 pm   #3
David G4EBT
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Default Re: Which BF245 FET to use?

The differing charcteristics are listed in the datasheet here.

http://pdf1.alldatasheet.com/datashe...ENS/BF245.html

Hope that helps a bit.

I wouldn't have thought that in such a simple circuit there'd be any discernable difference whichever version BF245 you used, but that's just my view.

Best of luck with the project.

David
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Old 12th Feb 2011, 9:59 pm   #4
murphyv310
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Default Re: Which BF245 FET to use?

It really should make little difference as the lads have said.
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Old 12th Feb 2011, 10:00 pm   #5
Bertusvz
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Default Re: Which BF245 FET to use?

Hello,

The drain current is diffrent when Vgs = 0.(see attachement).

I think the difference will hardly be noticed in your circuit.

Greetings,
Bertus
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