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Below is the block diagram of my first design using an audio power amplifier.

The input to the audio power amplifier comes from an SC200 module by Quectel.

The output of the PA is connected to a speaker.

I have couple of questions:

  1. Will the PA I selected w be able to drive this 4 ohm speaker?
  2. What are the things to be considered when selecting the PA for driving a speaker?
  3. How much power will I get at the output?
  4. In digikey during PA selection I can see that, Max Output Power x Channels @ Load is "3W x 1 @ 4Ohm" May I know what you mean by this?
  5. What will happen if I used the PA with above spec to 8 ohm speaker

enter image description here

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  • \$\begingroup\$ @tobalt,Desired loudness is not used,this speakers are used in our EV(bike) to give some notifications.The SC200 can support max 3W \$\endgroup\$
    – Confused
    Commented May 26, 2023 at 8:49
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    \$\begingroup\$ 4. At 5 V Vdd. 5. Assume half. Do you know how to calculate power according to Ohm's law? Do you know how to calculate the RMS value of a sine wave for a given peak voltage? \$\endgroup\$
    – winny
    Commented May 26, 2023 at 9:03
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    \$\begingroup\$ "5. What (watt?) happens with an 8 Ω speaker" It's the next entry in the datasheet from that quoted by tobalt - 680 mW minimum at 1% THD&N. The datasheet is your friend; read it thoroughly. Note the small print surrounding any parameters you wish to use. You'll need to recreate those conditions to achieve the stated parameters. \$\endgroup\$
    – Graham Nye
    Commented May 26, 2023 at 9:18

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The datasheet gives pretty precise information:

enter image description here

If it could output the full supply voltage as Vpk, then the power would be a bit higher (closer to 2 W), but Delta Sigma PAs of modulation order higher than 2 have a maximum stable relative amplitude, which they cannot exceed for stability reasons.

Driving this 2 W speaker with 1.2 W sounds like a nice balance of loudness and headroom, and a "good" (as far as possible with such speaker) recipe for good audio reproduction.

If you want the full 3 W into 4 Ω, you will need a higher supply voltage as shown also in the datasheet Fig. 10:

enter image description here

Fig. 11 shows what to expect with an 8 Ω speaker. The power will be lower as expected, but most often, 8 Ω speakers can have a higher sensitivity (more loudness per power), so you must calculate loudness for each speaker and its corresponding sensitivity.

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  • \$\begingroup\$ Thank you.I edited the question.Added two more questions.If you don't mind could you please check \$\endgroup\$
    – Confused
    Commented May 26, 2023 at 8:58

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