APA4838 Ver la hoja de datos (PDF) - Anpec Electronics

Número de pieza

componentes Descripción

Fabricante

APA4838

Stereo 2.8W Audio Power Amplifier with DC Volume Control and Selectable Gain

Anpec Electronics 

APA4838

Application Descriptions

BTL Operation

BTL Operation (Cont.)

The APA4838 output stage (power amplifier) has two A BTL amplifier design has a few distinct advantages

pairs of operational amplifiers internally, allowed for over the SE configuration, as it provides differential

different amplifier configurations for each channel. drive to the load, thus doubling the output swing for a

Gain 1

Gain 2

specified supply voltage.

Four times the output power is possible as compared

Volume Control

Am plifier output signal

OP1

-Out

to a SE amplifier under the same conditions. A BTL

configuration, such as the one used in APA4838, also

creates a second advantage over SE amplifiers.

RL Since the differential outputs, +Right Out, -Right Out,

+Out

+Left Out, and -Left Out, are biased at half-supply,

Vbias

OP2

no need DC voltage exists across the load. This elimi-

Figure 1: APA4838 power amplifier internal configu- nates the need for an output coupling capacitor which

ration (each channel)

is required in a single supply, SE configuration.

The power amplifier OP1 gain is setting by internal

unity-gain or external gain setting which is selected

from Gain Select pin and the audio input signal come

from internal volume control block, while the second

amplifier OP2 is internally fixed in a unity-gain, in-

verting configuration. Figure 1 shows that the output

of OP1 is connected to the input to OP2, which re-

sults in the output signals of with both amplifiers with

identical in magnitude, but out of phase 180°.

Consequently, the differential gain for each channel

is 2X (Gain of SE mode).

By driving the load differentially through outputs -Out

Single-Ended Operation

Consider the single-supply SE configuration shown

Application Circuit. A coupling capacitor is required

to block the DC offset voltage from reaching the load.

These capacitors can be quite large (approximately

33µF to 1000µF) so they tend to be expensive, oc-

cupy valuable PCB area, and have the additional

drawback of limiting low-frequency performance of

the system (refer to the Output Coupling Capacitor).

The rules described still hold with the addition of the

following relationship:

and +Out, an amplifier configuration commonly re-

ferred to as bridged mode is established. BTL mode

1

Cbypass x 125kΩ

≤

1 << 1

RiCi RLCC

(1)

operation is different from the classical single-ended

SE amplifier configuration where one side of its load

is connected to ground.

Copyright  ANPEC Electronics Corp.

17

Rev. A.1 - Apr., 2003

www.anpec.com.tw

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