TDA7404D

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1.0 DESCRIPTION OF FUNCTIONALITY

1.1 Input stages

Most of the input stages have remained the same as in preceding ST-Audioprocessors with exception of the

CD-inputs (see Figure 1). In the meantime there are some CD-players in the market which have a significant

high source-impedance which effects strongly the common-mode-rejection of the normal differential input stage.

The additional buffer of the TDA7404D Diff

-input avoids this drawback and offers the full common-mode-rejection even with those CD-players.

Figure 1. Input-stages

Note. It is possible that the Differential input is switched a single ended input (SE4) like SE1.. 3.

1.2 AutoZero

In order to reduce the number of pins there is no AC coupling between the In-Gain and the following stage, so

that any offset generated by or before the In-Gain-stage would be transferred or even amplified to the output.

To avoid that effect a special Offset-cancellation-stage called AutoZero is implemented. This stage is located

Diffin+

/(SE4)

Ingain

28k

28k

28k

28k

Diffgnd

Mono+

Mono -

SE1

SE2

SE3

10

0k

10

0k

10

0k

10

0k

10

0k