0V

-12V

+12V

Current

OUTP

OUTN

Differential

Voltage

Across

Load

0V

-12V

+12V

Current

OUTP

OUTN

Differential

Voltage

Across

Load

Output=0V

Output>0V

TPA3111D1

CLASS-D OPERATION

This section focuses on the class-D operation of the TPA3111D1.

TPA3111D1 Modulation Scheme

The TPA3111D1 uses a modulation scheme that allows operation without the classic LC reconstruction filter

when the amp is driving an inductive load. Each output is switching from 0 volts to the supply voltage. The OUTP

and OUTN are in phase with each other with no input so that there is little or no current in the speaker. The duty

cycle of OUTP is greater than 50% and OUTN is less than 50% for positive output voltages. The duty cycle of

OUTP is less than 50% and OUTN is greater than 50% for negative output voltages. The voltage across the load

losses in the load.

Figure 18. The TPA3111D1 Output Voltage and Current Waveforms Into an Inductive Load

Ferrite Bead Filter Considerations

Using the Advanced Emissions Suppression Technology in the TPA3111D1 amplifier it is possible to design a

high efficiency Class-D audio amplifier while minimizing interference to surrounding circuits. it is also possible to

accomplishthis with only a low-cost ferrite bead filter. In this case it is necessary to carefully select the ferrite

bead used in the filter.

One important aspect of the ferrite bead selection is the type of material used in the ferrite bead. Not all ferrite

material is alike, so it is important to select a material that is effective in the 10 to 100 MHz range which is key to

the operation of the Class D amplifier. Many of the specifications regulating consumer electronics have

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