OPAMP

Co

Mute Circuit

Output

MUTE

9-12 V

+

+

+

-

TPA6139A2

Output

3.3 V

-

Conventional solution

TPA 6139 A 2 Solution

VDD

VSS

GND

VDD

VDD/2

GND

DirectPath

MUTE

TPA6139A2

www.ti.com

SLOS700B – JANUARY 2011 – REVISED JUNE 2012

APPLICATION INFORMATION

LINE DRIVER AMPLIFIERS

Single-supply line-driver amplifiers typically require dc-blocking capacitors. The top drawing in Figure 9 illustrates

the conventional line-driver amplifier connection to the load and output signal.

DC blocking capacitors are often large in value, and a mute circuit is needed during power up to minimize click

and pop. The output capacitor and mute circuit consume PCB area and increase cost of assembly, and can

reduce the fidelity of the audio output signal.

Figure 9. Conventional and DirectPath Line Driver

The DirectPath™ amplifier architecture operates from a single supply but makes use of an internal charge pump

to provide a negative voltage rail.

Combining the user-provided positive rail and the negative rail generated by the IC, the device operates in what

is effectively a split supply mode.

The output voltages are now centered at zero volts with the capability to swing to the positive rail or negative rail.

Combining this with the built-in click and pop reduction circuit, the DirectPath™ amplifier requires no output dc

blocking capacitors.

The bottom block diagram and waveform of Figure 9 illustrate the ground-referenced line-driver architecture. This

is the architecture of the TPA6139A2.

Copyright © 2011–2012, Texas Instruments Incorporated

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