Hi pico,
I probably would use the pucks for the reasons you quoted plus several others in this circuit..
Cascoding does solve these issues...look at input capacitance and the circuit used to drive them. I think the original devices chosen plus drivers are the solution....but that is only my opinion.
Jam
PS. Are you still in the states or back down under?
I probably would use the pucks for the reasons you quoted plus several others in this circuit..
Cascoding does solve these issues...look at input capacitance and the circuit used to drive them. I think the original devices chosen plus drivers are the solution....but that is only my opinion.
Jam
PS. Are you still in the states or back down under?
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Hi pico,
I probably would use the pucks for the reasons you quoted plus several others in this circuit..
Cascoding does solve these issues...look at input capacitance and the circuit used to drive them. I think the original devices chosen plus drivers are the solution....but that is only my opinion.
Jam
I am not in disagreement with your suggestions.
We weren’t discussing capacitance issues.
I was just pointing out puck selection is important to make sure you don’t buy ones that will fail due to hotspots.
Even though cascoding will make them easier to drive, the reason he went to cascoding was because I suggested he should reduce the Vds value.
I think bridging would be a better solution (to reduce Vds) and maybe adding a driver stage if necessary like you suggested.
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Here is Ixys Appplication Notes IXAN0068.pdf titled "Linear Power MOSFETS Basic and Applications" for reference.
I have also reached the conclusion that BuzzBomb really can't avoid drivers, whether using pucks or not.
Sorry Jam, I'm just slow.
I was originally trying to stay with 3 stages, but drivers aren't really a stage anyway, as they're just emitter followers. Do I have that right?
I'll get back to the puck questions after doing some more reading, particularly Indrawan's link and I suspect there's some good stuff in the F4 Beast Builders thread....
Cheers,
Jeff.
Sorry Jam, I'm just slow.
I was originally trying to stay with 3 stages, but drivers aren't really a stage anyway, as they're just emitter followers. Do I have that right?
I'll get back to the puck questions after doing some more reading, particularly Indrawan's link and I suspect there's some good stuff in the F4 Beast Builders thread....
Cheers,
Jeff.
I think Jam's post is missing a "n't" after the "would". But in any case my further reading on pucks just means I'm not going to go any further with them at present (in any topology).
Anyhoo, without further ado I present BuzzBomb, complete with high-frequency performance and short circuit survivability:
I note that Goldmund used a completely different compensation strategy, which didn't require the hammer I used on the second differential. I'm going to play around with that next....
(But the above is stable, at least in SPICE.)
Just go right to the end of the article.
There is a list of parts that don’t suffer from the failure mechanism I mentioned.
I think there might be a couple more I can add to the list.
In F4 beast builders we were only looking at 25V to 30V Vds and lower thermal dissipation (although same currents), this issue was less of a problem for us, so we kept our FAB titles intact
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The way you should think about it is, “will adding this extra stage add much additional distortion”
A driver stage generally won’t add much additional distortion but you should make sure your circuit is setup correctly to minimise any additional distortion from the addition of drivers.
That’s not too hard thankfully, just something to be aware of.
I always prefer a 3 stage amp too, but try it both ways.
The driver stage will make the amp an animal that can essentially drive anything.
Sometimes making something too simple has a price and vice versa.
You have to look at the application and design goals and in this case topology limitations. That said, all things being equal simpler is better.
Jam
PS. I rate cascodes as half a stage...... if the number of stages is important.
You have to look at the application and design goals and in this case topology limitations. That said, all things being equal simpler is better.
Jam
PS. I rate cascodes as half a stage...... if the number of stages is important.
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