You would like to build a custom speaker system for your cell phone. The signals from the headphone jack are GND$,$ Left Channel, and Right Channel.

You find a speaker test tone app that send a constant tone to each channel.

Turning the volume to its maximum setting, you measure the voltage between the Left Channel and GND to be $2$ V $.$ You see a similar voltage when you measure between the Right Channel and GND$.$

You will be connecting the left channel to an $8,50$ Watt speaker. You will connect the right channel to another $8,50$ Watt speaker.

Connecting the right or left channel, at maximum volume, directly to a speaker only gives:

$P=\frac{V^2}{R}=\frac{2^2}{8}=500mW$ of power.

In a $50$ Watt speaker, this isn't enough power to move the diaphragm $($no sound$).$

Assuming we want the speaker voltage to be in$-$phase with the phone voltage and we want $50$ Watts of power at maximum cell phone volume, what amplifier topology, gain, and power rails would be required for each channel?

NOTE: Don't try this at home!! Depending on your power rails, the amplifier would be required to dissipate $>50$ Watts of power. Most commercially available amplifiers will $($best case$)$ smoke and flame or $($worst case$)$ explode at this power level! For the LM$741$ amplifiers used in Lab $7,$ the maximum power is $500$ mW $($from datasheet$).50$ Watts is $100$ X the maximum power level the amplifier can handle. In addition, the resistors used in the lab are rated at $0\mathrm{.}25$ Watts, so doing this experiment would cause catastrophic failure in every part of the circuit.

I suggest purchasing a speaker designed for this use. It will come with amplifier circuitry built in$.$

Select one:

a$.$ Two amplifiers are required. One for each channel. The left channel will require an inverting amplifier with gain of $10$ and power rails of $\frac{+}{-}15$ V $.$ The right channel will require a non$-$inverting amplifier with gain of $11$ and power rails of $\frac{+}{-}20V.$

b$.$ Two amplifiers are required. One for each channel, but they will be the same. A non$-$inverting amplifier topology with gain of no more than $10$ and power rails of $\frac{+}{-}25V$

c$.$ A single amplifier is all that is required, but it would be required to provide $100$ Watts of power. A non$-$inverting amplifier connected to both the left and right channel with gain of $100$ and power rails of $\frac{+}{-}210V.$

d$.$ Two amplifier are required. One for each channel, but they will be the same. A inverting amplifier topology with gain of $9$ and power rails of $\frac{+}{-}20V$