TDA7404 ST Microelectronics, TDA7404 Datasheet - Page 8

• Manufacturer Part Number: TDA7404
• Description: CARRADIO-SIGNAL-PROCESSOR
• Manufacturer: ST Microelectronics

TDA7404D
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
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D i f f i n +
/ ( S E 4 )
D i f f g n d
M o n o +
M o n o -
S E 1
S E 2
S E 3
1 0
0 k
1 0
0 k
1 0
0 k
1 0
0 k
1 0
0 k
2 8 k
2 8 k
2 8 k
2 8 k
I n g a i n