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Old 12th February 2010, 02:40 PM   #1
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Default Simple 15-25W amp on 12VDC?

I'm curious if there are any class D chips out there that allow for a simple design and can run on 12VDC and produce somewhere between 15 and 25 Watts? This will be powered by a PC power supply and does not have to be audiophile quality but would like it to sound as good as possible.

If no such Class D chip exists I was leaning towards using a TDA1554 (or perhaps the TDA8566 which is in the current product lineup). The Class D appeals to me due to lower heat and power consumption. Circuit doesn't have to be as simple as the one for TDA1554 but I need it to be inexpensive and easy to assemble.

The specs for the TA2020 look perfect for this but I was really wanting something simpler requiring fewer components.
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Old 12th February 2010, 09:58 PM   #2
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Sorry, but "simple" and "Class-D" don't really go together; at least not in the same sense as a "simple" Class-AB chipamp (more to do with layout than component count).

To get 15-25W RMS from a 12V supply, you will need a fairly low impedance load. You can get that power range with a 4R load at about 10% distortion though.

The "simplest" Class-D chipamp I have built uses the TPA3122D2. It will need to be bridged to get the power you want though.

My TPA3122D2N BTL proto

Digital Amplifier Solutions - Analog-Input Class-D Speaker Amplifiers - TPA3122D2 - TI.com

Last edited by theAnonymous1; 12th February 2010 at 10:01 PM.
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Old 13th February 2010, 12:32 AM   #3
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That's what I figured after taking a look at quite a few schematics for class D. Thanks for the response. It will help in my decision on what direction to take with this. I'd love to do Class D for this but Class A/B probably makes more sense for this application and price point.
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Old 13th February 2010, 12:37 AM   #4
bwaslo is offline bwaslo  United States
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Or you could buy one of a number of prebuilt Tripath based amps off ebay for about what the chip would cost you. At 4 ohms you might get close to 15W...
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Old 13th February 2010, 12:54 AM   #5
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Originally Posted by bwaslo View Post
Or you could buy one of a number of prebuilt Tripath based amps off ebay for about what the chip would cost you. At 4 ohms you might get close to 15W...
I still may go that route. I was looking to combine a few different applications onto one PCB for the sake of neatness and ease of wiring. I will be driving a 4ohm load and was definitely thinking of the absolute maximums when specifying 15-25Watts.
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Old 14th February 2010, 02:33 AM   #6
djk is offline djk
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25W at 4R is 28.28V peak-to-peak, a bit hard to get with a 12V supply without an inverter.

A/D/S made a bi-polar transistor amplifier with 25.3V peak-to-peak (20W/4R) with a bridged CFP output stage (with voltage gain) that ran on 13.8V (automotive 12V).
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Old 15th February 2010, 07:37 PM   #7
Eva is offline Eva  Spain
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Check TDA1562Q. This IC is class AB/H and includes a voltage doubler, so efficiency is better than class AB, and 4 ohm output power is 3 to 4 times what the usual 12V class AB or D amps would produce.
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Old 15th February 2010, 08:36 PM   #8
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Check TDA1562Q. This IC is class AB/H and includes a voltage doubler, so efficiency is better than class AB, and 4 ohm output power is 3 to 4 times what the usual 12V class AB or D amps would produce.

Interesting. Thanks!

Right now I'm leaning toward the TDA7376B simply because it comes in a multiwatt package which would be much easier to find heatsinks for. Is there an "off the shelf" heatsink available for the NXP chips like the TDA1562Q or TDA8566?
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Old 15th February 2010, 08:58 PM   #9
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I have a TDA7370B I recently pulled from an old powered PC 2.1 speaker setup. It should give close to the same power/performance as the TDA7376B.

You can have it if you want it. Giving it away will save me from starting another project I don't need.

TDA7370B Datasheet
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Old 18th February 2010, 08:13 PM   #10
rx7mark is offline rx7mark  United States
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A 41hz AMP6 basic will do this from 12v.

See 41Hz Audio:AMP6-BASIC kit

Here is a quote from the web page:

"The output power is around 2x25W RMS maximum, into 4 ohms at 10% THD+N. Up to about 2X15W, the THD+N is below 0.1%. "

Mark
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