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GE863-QUAD
1vv0300715 Rev. 1 - 19/09/06
8.6 Car Kit Speakerphone Design
For the car kit speaker phone function the power output requirement is usually at least 4W, therefore an amplifier is needed to boost the
The design of the amplifier shall comply with the following guidelines:
•The input to the amplifier MUST be taken from the “Ear_HF” audio path of the
•The amplifier shall have a gain of
•If the amplifier has a fixed gain then it can be adjusted to the desired value by reducing the input signal with a resistor divider network.
•The amplifier shall have a mute control to be used while not in conversation. This results in two benefits: eliminating the background noise when not in conversation and saving power.
•The power to the amplifier should be decoupled as much as possible from the
•The biasing voltage of the amplifier shall be stabilized with a low ESR (e.g. a tantalum) capacitor of adequate value.
NOTE: The
Example of car kit amplifier schematic.
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