Device Encapsulations

Gentlemen,

I've come across an RF transistor which seems to be available in 3 very different ecapsulations. I'll use these links from Ebay for simplicity and hope they're still up by the time anyone reads this. :-)

The first case appears to be based on the TO-220 dimensionos but appears to be all plastic:

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The second is what I would typically expect to see an RF transistor encased with:

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The final one is a conventional TO-220 with metal heat sink.

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The optimal casing is number 2, offering good thermal conductivity away from the device plus low parasitics.

The one with the conventional TO-220 provides heat sinking adequate for a device of this power rating, but is not so good on the parasitics. Fortunately these are only used up to about 30Mhz so presumably get-away-with-able.

I don't know what to make of the all plastic encapsulation, which seems to have nothing to recommend it. Any comments? Datasheet here:

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Reply to
Cursitor Doom
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That's a isolated to220, you dont need a mica insulator and ceramic washer. If your worried about thermals the use th rf power package.

There are newer rf parts you know.

Cheers

Reply to
Martin Rid

Yes, I know. I'm not planning on using one of these. I was just curious about the merits or otherwise of the 3 packages.

Reply to
Cursitor Doom

The insulated TO-220, I've seen in mass-market consumer low to mid-frequency, medium power circuits, where saving a few assembly steps (labor cost) & parts are key And also avoids stocking the thermally conductive-insulator pad (and/or possibly thermal grease).

Reply to
Rich S

It just seems fundamentally wrong to do such a casing for a power transistor. I know it's not really that powerful and won't create that much heat, but even so....sub-optimal IMO.

Reply to
Cursitor Doom

Everything is sub optimal. Mostly because things only need to be "good enough".

Reply to
Ricky

Wny? Cost in volume mfring.

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RL

Reply to
legg

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