TPA2000D4

STEREO 2-W CLASS-D AUDIO POWER AMPLIFIER

WITH STEREO HP AMPLIFIER

SLOS337A – DECEMBER 2000 – REVISED MAY 2003

21

POST OFFICE BOX 655303

APPLICATION INFORMATION

block the dc bias at the output of the amplifier, thus preventing dc currents in the load. As with the input coupling

capacitor, the output coupling capacitor and impedance of the load form a high-pass filter governed by

equation 14.

(14)

1

2

pR

The main disadvantage, from a performance standpoint, is that the typically small load impedances drive the

frequency response characteristics of each configuration.

Table 3. Common Load Impedances vs Low Frequency Output Characteristics in SE Mode

RL

CC

Lowest Frequency

32

Ω

68

µF

73 Hz

10,000

Ω

68

µF

0.23 Hz

47,000

Ω

68

µF

0.05 Hz

As Table 3 indicates, headphone response is adequate and drive into line level inputs (a home stereo for

example) is very good.

The output coupling capacitor required in single-supply SE mode also places additional constraints on the

selection of other components in the amplifier circuit. With the rules described earlier still valid, add the following

relationship:

(15)

1

C

B

55 k

Ω

v

1

C

1

R

The TPA2000D4 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling

to ensure the output total harmonic distortion (THD) is as low as possible. Power supply decoupling also

prevents oscillations for long lead lengths between the amplifier and the speaker. The optimum decoupling is

achieved by using two capacitors of different types that target different types of noise on the power supply leads.

For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-resistance

(ESR) ceramic capacitor, typically 0.1

filtering lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10

µF or greater, placed near

the audio power amplifier is recommended.

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.

for the best THD and noise performance.