TPA3139D2: How to Reducing Gain at the input of Audio Amplifier

Sha

Part Number: TPA3139D2
Other Parts Discussed in Thread: TLV320AIC3106

Hi TI Experts,

We are planning to connect TLV320AIC3106 (CODEC) to the audio amplifier (TPA3139D2). The analogue output from CODEC (on the pin LEFT_LOP) is connected to the audio amplifier as single ended. We are setting up the gain of CODEC channel at 0dB (synthetic gain). The gain of the TPA3139D2 is fixed at 20dB. But our required gain at the output of the audio amplifier is 16dB. I am attaching the reference schematic picture below, My question is,

How to reduce the gain at the input of audio amplifier to -4dB without compromising any audio performances to adjust the audio amplifier output gain to the required level16dB?
What are the methods or techniques used for reducing the gain at the input?

Best Regards

Sharvy

over 1 year ago

0 Yanming Gong over 1 year ago

TI__Mastermind 19250 points

Hi Sharvy,

I suggest that the best way is to add divided resistor between codec and AMP input caps. That is to reduce AMP input level.

Regards,

Derek

0 Sha over 1 year ago in reply to Yanming Gong

Prodigy 70 points

Hi Derek,

Can you please verify & confirm below resistor values are correct to produce -4dB attenuation on gain at the input of audio amp?
Also, please let me know what are the side effects which you think this solution might have?
Do you think, if we need any unity gain buffer (op-amp) after this divider network?

0 Yanming Gong over 1 year ago in reply to Sha

TI__Mastermind 19250 points

Hi Sharvy,

The solution is fine, it has no other bad effects.

For last question, do you mean the AGL?

Regards,

Derek

0 Sha over 1 year ago in reply to Yanming Gong

Prodigy 70 points

Hi Derek,

I am talking about unity gain buffer amp to avoid any impedance discontinuities.

Best Regards

Sha

0 Shadow He over 1 year ago in reply to Sha

TI__Mastermind 34480 points

Hi Sha

Sha said:
I am talking about unity gain buffer amp to avoid any impedance discontinuities.

Best Regards

Needn't to do this, our device is designed to drive speaker directly. Also if you use a linear amp as the gain buffer, it's efficiency is very low, usually can't output very large power.

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TPA3139D2: How to Reducing Gain at the input of Audio Amplifier