TPA3122 for driving external MOSFET's - diyAudio
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Old 16th April 2010, 06:28 PM   #1
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Default TPA3122 for driving external MOSFET's

Hi.
I'm trying to drive some external MOSFET's with the TPA3122 class-D chip. I hooked up the chip on the breadboard and got it working just fine.
Then I configured a half-bridge setup using IRFZ48N and IRF5305. It works just fine, and by using a simple LM317 regulator I tried to run with +/- 25 volt. Way over the TPA3122 ratings.
But I don't get more power from my external MOSFET's even with 50volt than if I just used the chip alone. The only difference there is, is that I can drive with low impedance, but still no more power ;(
I think I have a wrong circuit for driving the external MOSFET's:

How do I connect it correctly?

Regards,

Simon H.A.
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Old 22nd April 2010, 09:59 PM   #2
jej is offline jej  France
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Hi,
It's logic! It's a voltage follower. I don't know the TPA3122 but I think It's possible with outputs to "attack" a driver (TC4420 for instance) followed by a classical half bridge topology supplied by a symetrical voltages
Regards
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Old 23rd April 2010, 11:22 AM   #3
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You can drive a lower impedance, ergo more power at the same voltage!

BTW, if you have a P-channel device at the top of the totem pole, then D1 is the wrong way round! (The diodes should be connected to turn the MOSFETs off quickly, but let them turn on through the 15R resistors.)
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