This is for a low voltage power amp, say 10kHz to 100kHz, maybe 2A peak from 5V or 3V3 supply.
Things like FMMT617 and FMMT717 simulate very well, but they're only SOT23. As I need to run this at a high ambient temperature, I need something with much pore power dissipation. Even using multiple SOT23's won't cut it.
Any suggestions?
-- Cheers Clive
Mosfet or GaN. Bipolars will have a lot of switching loss, not to mention base current. 2 amps from a SOT23 fet, or a BGA GaN, would be easy.
-- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Sorry, linear amplifier, should have said.
-- Cheers Clive
How low are you looking for?
There are packages much better thermally but not much larger than SOT23. I was planning to use this part in a 2 mm sq package with thermal pads. Rds in the teens of mOhms.
There should be plenty of bipolar parts in the same type of packaging. Digikey is better than Google for this sort of search.
-- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
Clive,
It would be helpful to know much more about this linear wide-band design spec and load impedance (f) rather than the parts that don't work.
I suspect you are implying ~ 1 Ohm but what L,R values or datasheet.
This then poses problems for AC coupling single supply with a need for > 1mF
What non-linearity specs? THD, asymm. etc.
I suggest you need a list of design goals and specs clearly list first.
Implementation will be multiple choice TBD.
This is the hardest lesson to learn in design. Write good specs 1st. But you can learn by reading them from commercial datasheets.
Depending on your THD requirements, you could go class D on it
That will run cool
Cheers
Klaus
Oh. "Saturation" sounded like switching. But you still might consider mosfets. Even little ones turn on to a few milliohms.
-- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
PBSS303NX, PX and friends?
Is there a power opamp with RRO and slightly above average power bandwidth?
Class D isn't completely ruled out as it could be buzzing at low MHz, possibly GaN based. Would have to shop around. Downside is, such chips are often highly specialized, so maybe it only accepts I2S audio, or has internal filtering, or something, or maybe you just don't want to proto with a This is for a low voltage power amp, say 10kHz to 100kHz, maybe 2A peak
The gotcha is "mounting pad for drain 6 cm2"
Sylvia.
What is the topology ? A single ended class-A common emitter stage ?
With that low supply voltage an inductive collector load should help increasing the voltage swing. Either a transformer coupling or a choke to V+ and output voltage from the collector.
Why is that a "gotcha"??? That's the heat sink. Much less expensive than bolting to a hunk of aluminum. How else would you expect to get rid of heat???
You do realize you can put the copper area on the other side of the board in the form of a ground plane, right? A dozen or so vias and you have effective coupling.
-- Rick C. + Get 1,000 miles of free Supercharging + Tesla referral code - https://ts.la/richard11209
Interesting, thanks.
Anything complicated usually has thermal shutdown, which rules it out. This is for 180'C ambient...
-- Cheers Clive
Thank, yes I've looked at those. Maybe two in parallel, and their thermal shutdown is optional for a change. It's a higher risk but a simpler solution, so may be worth testing some at higher ambient temps.
-- Cheers Clive
-------------------
** Totally insane.
Yes, gas mark 4. Limited lifetime, but it's not usually 180'C for more than a few hours at a time, but it does take some hours to get there and back.
-- Cheers Clive
That rules out most plastic devices. They're usually rated for
They may well be /rated/ for 150'C (or even 85'C) that doesn't necessarily stop them working at 180'C. People who do this work have a jealously-guarded list of parts which are known to operate at high temperatures, often with some limitations. Plastic packages aren't a problem particularly, in fact they may even be better than ceramic in that they can flex just a little.
-- Cheers Clive
Nice part, similar to OPA547; pity it's basically 5 volts.
Interesting how they avoid discussing capacitive loads. That's usually a flag that they don't want to reveal something, and want thousands of users to discover it independently at great expense.
Why does TI use such crazy file names?
-- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
11 amps, for 5 seconds! With 10 volts of gate drive! No details about that pad, either.
If a thing like that is hard switching a few amps at low rates, power dissipation will be tolerable. But getting any amount of power out of a package that small is a pain. Thermal spreading resistance of a copper pour, from the tiny power pad, will be a limit on cooling.
6 cm2 of copper, may as well use a DPAK! Easier to solder and probe, too.-- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
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