TPA751

700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

WITH DIFFERENTIAL INPUTS

SLOS336C – DECEMBER 2000 – REVISED OCTOBER 2002

18

POST OFFICE BOX 655303

APPLICATION INFORMATION

function is to reduce noise produced by the power supply caused by coupling into the output drive signal. This

noise is from the midrail generation circuit internal to the amplifier, which appears as degraded PSRR and

THD + N. The capacitor is fed from a 250-k

Ω source inside the amplifier. To keep the start-up pop as low as

possible, the relationship shown in equation 10 should be maintained. This insures the input capacitor is fully

charged before the bypass capacitor is fully charged and the amplifier starts up.

(10)

10

C

B

250 k

Ω

v

1

R

F )

R

I

C

I

values into the equation 10 we get:

18.2

v 35.5

are recommended for the best THD and noise performance.

using low-ESR capacitors

Low-ESR capacitors are recommended throughout this applications section. A real (as opposed to ideal)

capacitor can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this

resistor minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this

resistance, the more the real capacitor behaves like an ideal capacitor.

5-V versus 3.3-V operation

The TPA751 operates over a supply range of 2.5 V to 5.5 V. This data sheet provides full specifications for 5-V

and 3.3-V operation, as these are considered to be the two most common standard voltages. There are no

special considerations for 3.3-V versus 5-V operation with respect to supply bypassing, gain setting, or stability.

The most important consideration is that of output power. Each amplifier in TPA751 can produce a maximum

an 8-

Ω load before distortion becomes significant.

Operation from 3.3-V supplies, as can be shown from the efficiency formula in equation 4, consumes

approximately two-thirds the supply power of operation from 5-V supplies for a given output-power level.