TPA0211

2-W MONO AUDIO POWER AMPLIFIER

SLOS275D – JANUARY 2000 – REVISED NOVEMBER 2002

13

POST OFFICE BOX 655303

APPLICATION INFORMATION

Table 1. Common Load Impedances vs Low Frequency Output Characteristics in SE Mode

RL

C(C)

Lowest Frequency

3

Ω

330

µF

161 Hz

4

Ω

330

µF

120 Hz

8

Ω

330

µF

60 Hz

32

Ω

330

µF

15 Hz

10,000

Ω

330

µF

0.05 Hz

47,000

Ω

330

µF

0.01 Hz

As Table 1 indicates, most of the bass response is attenuated into a 4-

Ω load, an 8-Ω load is adequate,

headphone response is good, and drive into line level inputs (a home stereo for example) is exceptional.

Furthermore, the total amount of ripple current that must flow through the capacitor must be considered when

choosing the component. As shown in the application circuit, one coupling capacitor must be in series with the

mono loudspeaker for proper operation of the stereo-mono switching circuit. For a 4-

Ω load, this capacitor must

be able to handle about 700 mA of ripple current for a continuous output power of 2 W.

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.

bridged-tied load versus single-ended mode

Figure 22 shows a Class-AB audio power amplifier (APA) in a BTL configuration. The TPA0211 BTL amplifier

consists of two Class-AB amplifiers driving both ends of the load. There are several potential benefits to this

differential drive configuration, but initially consider power to the load. The differential drive to the speaker

means that as one side is slewing up, the other side is slewing down, and vice versa. This, in effect, doubles

the voltage swing on the load as compared to a ground referenced load. Plugging 2

equation, where voltage is squared, yields 4

× the output power from the same supply rail and load impedance.

(See equation 7.)

Power

+

V

(RMS)

2

R

L

(7)

V

(RMS

) +

V

O(PP)

22