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Q: Class AB amplifier efficiency in SE configuration
A customer wants to use a TPA711 in SE mode to drive a 15 Ohm speaker. Could you provide some design equations for calculating the efficiency of the audio amp and also the average current drawn so that i can calculate the amplifier dissipation. There is a detailed calculation for BTL in the datasheets.
A: Re: Class AB amplifier efficiency in SE configuration
The equations for efficiency for BTL and SE are the same except for the IDDrms calculation. For SE, IDDrms = Vp/(pi*RL) or half the value for BTL. This will make the amplifier twice as efficient as BTL for the same output power. Keep in mind these equations are only valid for sine waves and they assume the user has gotten rid of the DC current that will be flowing in single ended configuration. This can be done by using a DC blocking cap or tying the other end of the speaker to Vdd/2 instead of ground.
If this DC current is not removed, then an additional power dissipation of Vdd^2/RL will be occur, which will cause a drop in the efficiency of the system..
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