I'm looking at the PAM8406 Class-D/Class-AB amplifier and I'm not seeing the efficiency for a 2Ω load in Class-AB mode. The use case for the amplifier is driving mid-range/mid-bass speakers for use with a telephony system (essentially, no music will be output from the amp, and it will only be on for short a duration of time).

From what I've read, Class-D amplifiers are better suited to drive sub-woofers and other bass intensive applications, where as Class-AB is less efficient but more suitable for general audio applications.

  • How can I calculate the efficiency of this amplifier?
  • Is there a more suitable alternative to this amplifier for my use case? I need at least 2W into a 2-Ω load.
  • 2
    \$\begingroup\$ "What I've read, class-D … are better suited to drive … bass, whereas class-AB is less efficient but more suitable for general audio" I don't share that sentiment. Class D works fine for high audible frequencies, too. \$\endgroup\$ – Marcus Müller May 20 '19 at 21:45

This part is unique with no filter and optional dual class D or AB with differential drive , no pops and 4W from 5Vdc into 2 Ohms.

Since both Pch,Nch class D drivers are each less than 10% of 2 Ohms the losses are 20% max with 2Ohm speaker and 10% max with 8 Ohms.

η Efficiency Class D Mode f = 1kHz

RL =8Ω,THD=10% 90%
RL =4Ω,THD=10% 85%
RL =2Ω,THD=10% 80%

Class AB is always much less than 65% depending on peak to RMS crest factor


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