I'm working on a project that needs to drive a single speaker. I've used LM2879T chips in the past to drive two speakers, so I have a couple extra I'm trying to use for this single speaker project.

Since I'm using a single speaker, I've heard I should 'bridge' the two outputs of the amplifier. From the datasheet, it gives this example circuit. Maybe it is a silly question, but I'm not sure where I'm supposed to attach the speaker in this scenario. My best guess is that it takes the place of RL, but I wanted to check with others first. enter image description here

Elsewhere in the datasheet, it gives this example for a typical two speaker setup, and it is fairly obvious where the speakers go. enter image description here

Again, I'm using this chip just because I have it on hand. I've been eyeing some better options I would go for instead if this chip isn't worth it.

Thanks for any help!

  • 2
    \$\begingroup\$ I think the speaker is being modelled by that RL and the 2.7Ohms and 0.1uF in the center. \$\endgroup\$
    – DKNguyen
    Commented Mar 22, 2023 at 3:38
  • 4
    \$\begingroup\$ (@DKNguyen 2.7 Ω + 0.1 μF are the (hefty) Boucherot cell.) \$\endgroup\$
    – greybeard
    Commented Mar 22, 2023 at 3:49
  • 4
    \$\begingroup\$ The "L" subscript in "RL" stands for "load". \$\endgroup\$ Commented Mar 22, 2023 at 18:32

2 Answers 2


The speaker connects where RL is on your bridge amplifier chip. The app note says 16 ohms so you know that a 16 ohm speaker can be safely connected. If your intended single speaker is lower than 16 ohm like say 4 ohm or 8 ohm then check the fine print in the data sheet. Remember that all these audio chips are pretty much voltage sources so lower speaker impedences will mean that the chip will try to make more current. It might not be able to do this. It might shut down, it may die young.

  • \$\begingroup\$ Perfect, thanks! My next question was the about the impedence, but you have confirmed my suspicions. \$\endgroup\$
    – Gigaxalus
    Commented Mar 22, 2023 at 4:12

\$R_L\$ is the speaker (16ohms impedance!) and the capacitor/resistor across it are a Zobel network for reducing the reactive load on the amps.


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