I'm working to create a small amplifier using a single 12V supply. One (of several) limitations I have encountered is the necessary size of the output capacitors(1000uF to deliver 20Hz into 8ohm loads) and the associated power loss (1000uF @ 20Hz has nearly 8ohms impedance so it is using 50% of the output power).

Is there any Single Supply amplifier topology that does not require an output capacitor?

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    \$\begingroup\$ Yes - the bridge. \$\endgroup\$
    – user16324
    Commented Sep 19, 2017 at 21:07
  • \$\begingroup\$ To elaborate that a bit more: You use two amplifiers, feed one of them with an inverted signal and put the speaker between the two outputs. That's pretty standard for low-voltage high-power designs, e.g. in car stereos. So look for a "car stereo" schematic to get some ideas. \$\endgroup\$
    – Janka
    Commented Sep 19, 2017 at 21:25

1 Answer 1


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Figure 1. A typical bridge mode configuration.

Bridge mode amplifiers are popular in car audio systems. The output of each amplifier is biased to half-supply. (Since both sides of the speaker are at the same voltage in the quiescent state, no current will flow through the speaker.) One amplifier is fed directly with the signal while the other is driven with an inverted version. The output then "see-saws" about the mid-supply voltage.

  • \$\begingroup\$ +1, and these days you can get cheap bridged class-D amps also. \$\endgroup\$
    – bobflux
    Commented Sep 19, 2017 at 22:01

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