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Old 14th August 2010, 04:08 AM   #1
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Default amplify low frequency signal

Hi,
Not sure if this is the right place to ask this question.
I am trying to amplify a 0-1000 Hz sin signal to drive a 8 ohm EM load. I need the output power to be at least 20 W. Can a class D handle the job?
I saw all the specs only go down to 20 Hz.
Also, I would like the output to be zero if the input is zero.

Perticularly, can this

http://focus.ti.com/lit/ug/slou208/slou208.pdf

or this

http://focus.ti.com/lit/ug/slou210/slou210.pdf

work?

Thanks a lot in advance.
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Old 14th August 2010, 05:29 PM   #2
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The amps have input coupling capacitors. By increasing the value of those you can lower the low frequency cutoff. It shouldn't be a problem getting linear response down to 1Hz but you will also have to increase the power supply capacitance to have the amp deliver full power at such a low frequency.
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Old 14th August 2010, 05:41 PM   #3
Pafi is offline Pafi  Hungary
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Quote:
Can a class D handle the job?
Yes, but you need a DC coupled, bridged amplifier.
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Old 14th August 2010, 06:26 PM   #4
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...and Pafi is not just joking.
Full bridge is a key for DC-signal-applications, otherwise you will suffer from heavy rail pumping.
(A half bridge topology for DC-signals would demand a power supply, which can source and sink - normal power supplies can source only.)
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Old 14th August 2010, 08:12 PM   #5
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Thank you guys!
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Old 15th August 2010, 06:59 AM   #6
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Thank you.
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