APPLICATION INFORMATION

AUTOMATIC GAIN CONTROL

TPA2016D2

The Automatic Gain Control (AGC) feature provides continuous automatic gain adjustment to the amplifier

through an internal PGA. This feature enhances the perceived audio loudness and at the same time prevents

speaker damage from occurring (Limiter function).

The AGC function attempts to maintain the audio signal gain as selected by the user through the Fixed Gain,

Limiter Level, and Compression Ratio variables. Other advanced features included are Maximum Gain and Noise

Gate Threshold. Table 1 describes the function of each variable in the AGC function.

Table 1. TPA2016D2 AGC Variable Descriptions

VARIABLE

DESCRIPTION

Maximum Gain

The gain at the lower end of the compression region.

Fixed Gain

The normal gain of the device when the AGC is inactive.

The fixed gain is also the initial gain when the device comes out of shutdown mode or when the AGC is

disabled.

Limiter Level

The value that sets the maximum allowed output amplitude.

Compression Ratio

The relation between input and output voltage.

Noise Gate Threshold

Below this value, the AGC holds the gain to prevent breathing effects.

Attack Time

The minimum time between two gain decrements.

Release Time

The minimum time between two gain increments.

Hold Time

The time it takes for the very first gain increment after the input signal amplitude decreases.

Copyright © 2008, Texas Instruments Incorporated

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