# How is this figure supposed to be interpreted in the datasheet for the LM4766 audio amplifier, and determining the needed power requirements?

First off, I really have no experience when it comes to audio electronics, so forgive me if these are naive questions.

In any case, let me explain what I'm doing/trying to do. I have two speakers that can hand 25 watts (RMS) with a 50 watt max. The impedance of each is 8 Ohms.

Ohm's law gives us the simple equation P = V^2/R, so V = 20V when we're at our 50W max. Also, the speakers would draw 2.5A each.

I obviously need to amplify my audio source, and to this, I plan on using the LM4766 from Texas Instruments (Datasheet). According to the datasheet on page three, the supply voltage is defined to be |Vcc| + |Vee|, where Vcc is the positive supply voltage and Vee is the negative supply voltage. The max supply voltage is 60V.

Now here's my question. In figure 18 on page 10, pictured below, Output Power vs Supply Voltage is plotted. I find this plot somewhat ambiguous. Is it saying, for example, that if Supply Voltage = 25V (Vcc = 12.5V and Vee = -12.5V), then the output power is roughly 27W? Or is it saying that if Vcc = 25V and Vee = -25V, then the output power is roughly 27W?

Any input would be appreciated.

• Vcc = 25V and Vee = -25V. Ohm's law gives you peak power, not sustained; the graph has been built not with DC but with 1 kHz sine wave input. – ilkhd May 24 '15 at 1:35