TPA3255: Value of Input DC block capacitor for low frequency signal(Subwoofer)

Younggi Jung

Prodigy 40 points

Part Number: TPA3255

Tool/software:

Hello Mr or Mrs.

I am designing a subwoofer amplifier using TPA3255.

I have a question about a value of DC block capacitor (DBC).

DBC seems to act as a HPF. It seems that the evaluation board or generally uses 10uF for DC blocking. It seems to be suitable for general mid-range speakers, but I think it is not suitable for a subwoofer that generates relatively low-frequency sounds.

How can I determine the DBC to reproduce an input signal of about 25Hz to 300Hz?

2 days ago

0 Ramsey Foote 1 day ago

TI__Expert 8465 points

Hi Younggi,

You can calculate the low frequency cutoff using the input resistance of the amp and the capacitance of the DC blocking cap. On the TPA3255, the input resistance is 20k Ohm as mentioned in the datasheet. This means that with a 10uF DC blocking capacitance, you are looking at a cutoff frequency of f=1/(2*pi*C*R) = 0.8Hz.

Regards,

Ramsey

0 Younggi Jung 20 hours ago in reply to Ramsey Foote

Prodigy 40 points

I didn't consider input resistance. Hahaha

Thank you!

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TPA3255: Value of Input DC block capacitor for low frequency signal(Subwoofer)