Other Parts Discussed in Thread: TAS5414
I'm doing an audio power amplifier design using the TAS5414 quad Class D power amplifier. It's been several years since I last worked with Class D devices. They are now much faster (higher chop frequency) and have fewer parts than earlier designs.
In all early Class D amplifier designs there was always an LC filter between the amplifier's outputs and the speaker. The filter blocked the chopping waveform from reaching the speaker. In a time domain sense, the inductor in the LC filter integrated the PWM waveform much like the inductor in a buck converter.
Where is that LC filter in the documentation for the TAS5414 demonstration board? I see a twin-winding Toko common mode choke (HEAW) that is configured as a common mode filter. Presumably this choke prevents long speaker wires from radiating chopping carrier in the AM broadcast band.
However, the topology of a common mode choke does not permit it to filter ***differential*** chopping signal from reaching the speaker. It's a good common mode filter, but a terrible differential filter.
Jim Olson
Lafayette, IN US
