DD

P

SUP

L

V

V

P

R

2

=

p

P

P

P

SUP

DD DD

DD

L

L

L

V

V

V

P

V

I

avg and I

avg

t dt =

t

=

R

R

R

1

0

0

2

1

sin( )

[cos( )]

p

p

p

=

=

- ´

p

p

ò

L

P

P

L

LRMS

L

L

L

V rms

V

V

P

and V

=

therefore, P =

R

R

2

2

,

,

2

2

=

L

SUP

P

Efficiency of a BTL amplifier =

P

10

TPA6204A1

SLOS429C – MAY 2004 – REVISED MAY 2016

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Product Folder Links: TPA6204A1

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Copyright © 2004–2016 , Texas Instruments Incorporated

Feature Description (continued)

An easy-to-use equation to calculate efficiency starts out as being equal to the ratio of power from the power

supply to the power delivered to the load. To accurately calculate the RMS and average values of power in the

load and in the amplifier, the current and voltage waveform shapes must first be understood (see Figure 15).

Figure 15. Voltage and Current Waveforms for BTL Amplifiers

Although the voltages and currents for SE and BTL are sinusoidal in the load, currents from the supply are

different between SE and BTL configurations. In an SE application the current waveform is a half-wave rectified

shape, whereas in BTL it is a full-wave rectified waveform. This means RMS conversion factors are different.

Keep in mind that for most of the waveform both the push and pull transistors are not on at the same time, which

supports the fact that each amplifier in the BTL device only draws current from the supply for half the waveform.

Figure 13 and are the basis for calculating amplifier efficiency.

where

where

•

•

•

•

and

where

•

•

•

•

•

Therefore,

(2)