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Old 5th March 2009, 01:55 PM   #1
johnr66 is offline johnr66  United States
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Default No Boucherot cell?

Hello everyone! This is my first post.

I'm looking at low power chip amps for some projects. I see that many newer designs claim no Boucherot cell needed (lower power ICs). One chip I'm looking at is the 2+2 watt TDA7268 which requires very few external components that will keep costs down.

My question is how is the amp stabilized without the snubber network?

Also, some of these amps do without the bootstrap capacitor which used to be necessary on low voltage amps for a wider output swing.

Thanks for any enlightenment.
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Old 5th March 2009, 07:21 PM   #2
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Default Re: No Boucherot cell?

Quote:
Originally posted by johnr66
Also, some of these amps do without the bootstrap capacitor which used to be necessary on low voltage amps for a wider output swing.
The datasheet tells it: "fully complementary output configuration"
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Old 5th March 2009, 09:45 PM   #3
star882 is offline star882  United States
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Default Re: No Boucherot cell?

Quote:
Originally posted by johnr66
Also, some of these amps do without the bootstrap capacitor which used to be necessary on low voltage amps for a wider output swing.
It has to do with whether the amp is based on CMOS or NMOS. Pretty much all the smaller ones use CMOS so no charge pump is needed to drive the high side. NMOS amps need a charge pump to derive high side drive voltage, just like in a NMOS-based buck converter.

I'd recommend the TPA1517 for a beginner project. It is very, very simple to build, but runs hot at significant volumes. (I'm working on a design that uses a TPA1517 driving a transformer to generate ring voltage for a VoIP telephone line. Since it only operates for seconds each time, heat is not a concern.) Only 6 capacitors and a power supply needed to make the TPA1517 into a complete amplifier. (It is CMOS so no charge pump capacitors.)

For something a little more powerful, the TPA3122D2 is the best one I know of in DIP. It is much more powerful than the TPA1517 and actually runs cooler. (My friend actually built a very efficient amplifier based on two TPA3122D2s!) However, it needs a much more complex circuit to operate and is NMOS so it needs charge pump capacitors.
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