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View Full Version : OT- spec on this mosfet



darryl
02-11-2012, 09:42 PM
I have a fair number of this part no., and I'd like to be able to use them somewhere. I'd like to know what the specs are, but I'm having no luck finding this on the net. If you don't know, don't waste any time searching since you'll probably find the same 'datasheet not available' as I am. The part is a TO-220 mosfet 45F122. It comes off a power supply board from one of the flat screen tv's. I think it's made by Toshiba.

To guess from the usual practice of identifying parts like this, the first number would be the current capability, 45 amps in this case, and maybe 120 volts- not sure about this as the voltage rating though. It would be nice also to know the rds of this device.

Evan
02-11-2012, 09:53 PM
You can't find it because it is not a MOSFET. It's a IGBT. The part number is GT45F122. The rating is 45 amps, pulse 200 amps, 300 volt, n channel, serial number 22, version A

darryl
02-11-2012, 10:10 PM
That solves that one for me, thanks Evan. Looks like it will be useful.

Evan
02-11-2012, 10:39 PM
I forgot a spec or two. It's pretty fast. It will switch 400 amps per microsecond. Collector-emitter drop is a low of about 1 volt to a maximum of 2 volts at 50 amps with no change with temperature..

dp
02-11-2012, 10:49 PM
Those can be used to create amazingly powerful class D amplifiers. It would be kind of fun to build a 2KW audio amp. Not sure what your speakers would have to look like, but you'd have no trouble driving them. Reminds me of the opening of "Back to the Future" movie :)

darryl
02-11-2012, 11:04 PM
Looks like these might be ideal for controlling my electric trike motor. If I wire in four or five in parallel I should have no problem handling surge currents.

As far as the class D amplifier, you could go a step further and operate directly from rectified ac. I realize that puts the wiring, the voice coil and any matching networks at line potential, but you sure could get lots of power in a very light package. If the amp were built-in to the speaker cabinet, the only significant difference you'd have to make in the wiring is adding a ground wire to the speaker frame.

Some decades ago I was repairing console stereos. There was one model in the Philips brand that used 600 ohm speakers (usual is 8 ohms, sometimes 4 or 16 ohms). The speaker was directly driven from the tube amp without an output transformer. I was quite impressed with the sound quality from that. It did have a power transformer to get the operating voltages for the tubes, so it was isolated in that respect.

Operating directly from rectified ac, you could easily get a kilowatt into an 8 ohm speaker. You could use an opto- isolator based circuit to decouple the line voltage from your pre-amp, etc.

J Tiers
02-12-2012, 01:33 AM
As far as the class D amplifier, you could go a step further and operate directly from rectified ac. I realize that puts the wiring, the voice coil and any matching networks at line potential, but you sure could get lots of power in a very light package. If the amp were built-in to the speaker cabinet, the only significant difference you'd have to make in the wiring is adding a ground wire to the speaker frame.




You might need the speaker cone etc to be made of 94-V0 materials, which *might affect* the audio performance......

And you'd have to transfer the audio over some isolated "connection".... Would be best if the gate drive was the isolation, you can get good opto-isolated gate drivers from Avago (formerly HP)

A company had such an amplifier at the NAMM show many many years ago.... no transformers....... I asked them about that issue of being "live", and they assure me that the amp was referenced to the neutral "which is grounded"..... but then they sorta got quieter, and had a funny look in their eyes...... I never saw that company back at NAMM again.

darryl
02-12-2012, 02:38 AM
Everyone likes a good fire now and then, don't they? :)

That's a good point, JT. It's something I should have been considering along with the idea that's been in my head for some time now. It has to do with voice coils of a sort, and high power levels. If it went on fire, and there was a significant mass of combustible materials- well if this was a pa speaker in a well-attended venue with the chance of the cabinet becoming an inferno- I'll leave it at that.

We are talking about a flammability rating for materials, are we not? Otherwise I'm :o

Evan
02-12-2012, 04:13 AM
With those power levels you could make the speaker cone from honeycomb aluminum and wind the voice coil with 14 gauge. :D

Lew Hartswick
02-12-2012, 09:52 AM
With those power levels you could make the speaker cone from honeycomb aluminum and wind the voice coil with 14 gauge. :D
And use a megawatt magnetron magnet for the magnet. :-)
...lew...

Black_Moons
02-12-2012, 10:28 AM
And use a megawatt magnetron magnet for the magnet. :-)
...lew...

Thats for wussys, Real men buy surplused MRI machines to use as speaker magnets!

darryl
02-12-2012, 08:39 PM
And I once thought a 30 inch speaker was big. With those megawatts and magnetron magnet magnets, you could build a mondo macro money milking monster speaker!

Now I want to see the voice coil that uses 14 ga wire and is 8 ohms :)

Evan
02-12-2012, 08:41 PM
Why make it 8 ohms? How about 0.1 ohms? Of course you would have to connect it with jumper cables...

darryl
02-13-2012, 08:04 PM
No reason it needs to be 8 ohms. That figure probably allows for a voice coil wire size that's still workable, and matches the capability of an amplifier running fairly normal secondary voltages to deliver a respectable amount of power.

There's been many times when I worked with car stereo systems that I wondered why boost the 12 volts up to 30, 40, or whatever, just to be able to get the power into available speakers. Why not use a 1/2 ohm speaker and a bridge circuit directly from the 12v supply- sure the wire would have to be much larger gauge, and the flexible connection wire suitably 'fat' also- that's probably the weak link here, that flexible connection. Oh well.

J Tiers
02-13-2012, 09:35 PM
And also the pure mass of the voice coil....... physics imposes its restrictions......

Evan
02-13-2012, 09:44 PM
I think loudspeaker design is buried in the dark ages. The vast majority of low frequency speakers haven't changed appreciably in half a century. There must be room for improvement by moving away from traditional designs. We have magnets that are vastly more powerful than they were in the sixties. That alone gives a lot of room to move around with alternative designs.

darryl
02-14-2012, 01:13 AM
Hey, this is metal related- my tweeters are titanium domes!

J Tiers
02-14-2012, 08:27 AM
I think loudspeaker design is buried in the dark ages. The vast majority of low frequency speakers haven't changed appreciably in half a century. There must be room for improvement by moving away from traditional designs. We have magnets that are vastly more powerful than they were in the sixties. That alone gives a lot of room to move around with alternative designs.

Don't for a moment suppose that speakers far different from anything you know about are NOT being made..... There are so many types it boggles the mind.... And any type of magnet you can imagine has already been used.

But, many designs don't last long, they aren't practical, or work only in more limited ranges, etc, etc.

The common thread among most (but not all) is the interaction of current in a wire with a magnetic field.

That's hardly the only way to make a speaker, and different types NOT using that principle have been demonstrated, or even commercially made, for well over 100 years. But the old voice coil keeps coming around since it is one of the best compromises between manufacturability and predictable reproducibility of performance with efficiency and range.

people keep trying different things, and someday one may "stick".

I have seen probably 20 fairly different types of speaker in commercial production. Some close to traditional types, others radically different.

darryl
02-14-2012, 11:30 PM
There was one design made that used an air pump and a signal-operated valve to give an acoustic output.