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# TPA3116D2-Q1: Doubt about designing procedure

Part Number: TPA3116D2-Q1

Hello, thanks for taking the time for helping me with this doubt.

I want to design an audio power amplifier using the TPA3116D2-Q1. I had read the datasheet but is not clear to me the design procedure explained there. How should I do the calculation for identifying which of the gain should I use?

I want to design for two different kinds of load situations, both of them with mono output. For one of them, I have an RL = 4 ohm and the desired output power of 80 Wrms, the second option is an RL = 8 ohm and desired power of 40 Wrms.

How do I set the proper gain for the system to cover the desired output powers (there will be two conditions of output power that I should change with something like dip switches)? I´m not also clear how should I specify my required power supply voltage.

Thanks

• Sir,

The gain structure needed for your power levels, depends on the audio input level you can provide.  Please provide the input level and we can help you with setting the gain.

The power calculation on page 16 of the datasheet can be used to determine the power supply needed to meet your output power specs.

• Hi, actually I want to use as input a Bluetooth audio device output. I don´t know exactly which the input level is. I had done some search in the internet trying to find for some standard to obtain that data, but I had not found. At most, what I found was that for not professional audio devices, the jack 1/8 outputs devices can have levels around 0.774 V rms.

Would that be a good starting point? How those calculations are done?
• First determine the output voltage for 80W into 4 ohms and 40W into 8 ohms.  Use V^2/R =power to determine the output necessary.

The output Vrms will be 17.89Vrms for both 80W into 4 ohms and 40W into 8 ohms.

The gain needed for a 0.774Vrms input to get 17.89Vrms output is 23.1 V/V.  20*LOG(23.1)= 27.28dB of gain.  You can set the gain to 26dB or 32dB as shown in the datasheet.  This can be refined when you have the bluetooth audio device specs.

The power supply needed for 80W into 4 ohms will be same as 40W into 8 ohms.  The current capability of the power supplies will be different due to the power difference.

Using the graphs in Figure 13 and Figure 14, you can see that you need a 25V power supply to meet your needs.

• Thank you very much Gregg. One last question, those power values in the datasheet are RMS or peak values?

• Power rating is the average power.  Mathematically, there is no such thing as RMS Power or Peak Power.  It is just Power.

• Great, thank you very much for your help