replacement for FDT86256, can i use irf 510 or irf 520 ?

[reytek79]

Guys, I would like to know if there is any mosfet that can replace the FDT86256, can I use irf 510 or irf 520?

[LILO]

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[DL2MAN]

Guys, I would like to know if there is any mosfet that can replace the FDT86256, can I use irf 510 or irf 520?

IRF510 or 520 make very bad Class E PAs because of high Ciss and Coss and because they are slow. They need a lot of drive Power which the (tr)uSDX doesn´t have and add a lot of capacitance which de-tunes the filters.

If you want to know the details, there´s an excellent document, published by the master himself (Dan Tayloe, N7VE):
https://www.norcalqrp.org/files/Class_E_Amplifiers.pdf

You can substitute 1x FDT86256 by 3xBS170, they are close but not equal, so you still need to adjust your filters so you don´t produce harmonics and efficiency is high.

73 Manuel; DL2MAN

[reytek79]

Guys, I would like to know if there is any mosfet that can replace the FDT86256, can I use irf 510 or irf 520?

IRF510 or 520 make very bad Class E PAs because of high Ciss and Coss and because they are slow. They need a lot of drive Power which the (tr)uSDX doesn´t have and add a lot of capacitance which de-tunes the filters.

If you want to know the details, there´s an excellent document, published by the master himself (Dan Tayloe, N7VE):
https://www.norcalqrp.org/files/Class_E_Amplifiers.pdf

You can substitute 1x FDT86256 by 3xBS170, they are close but not equal, so you still need to adjust your filters so you don´t produce harmonics and efficiency is high.

73 Manuel; DL2MAN

OK Manuel I understand, I'm going to import the FDT86256 here in Brazil I can't find it, I asked about the IRF 510, 520 because I find them easy here in the local market, but as you mentioned that they are not good I will import the FDT86256 anyway.