Re: Sick SG504

Tom Lee

Thank you for the very helpful information, John. One thing that's always mystified me is that the Philips/NXP BFR94A doesn't even have the same die as the "original" BFR94A in the SOT122E. The breakdwon voltages, capacitances, max IC, ft, etc. are all different. I can't remember ever encountering a similar situation where the same transistor part number is used for such different devices (I'm excluding the data-compressed SMD marking codes).


Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070

On 2/8/2021 16:08, John Bennett wrote:
I misspoke regarding the package type for Q70 (I should have looked it up). You want the 4-tab studded package (it has two emitter tabs) referred to in various data sheets as SOT122E, SOT48, and I think TO-117 (not TO-128). In any event, the BFR94A in that form factor should work. I have also used the the Motorola MRF587 and MRF511 with some success, although there are trade offs:
Typ. fT (GHz) VCEmax (V) Max Diss (W) ICmax (ma)
BRF94A 3.5 25 3.5 300
MRF587 5.5 17 5 200
MRF511 2.1 30 5 250

I generally go with the BFR94A, which are usually easy to find on eBay.
Good luck with your project!

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