Speaker Interface Configuration - SimCom SIM900B Hardware Design

Smart Machine Smart Decision
AT command "AT+CMIC" is used to adjust the input gain level of microphone. AT command "AT+SIDET" is
used to set the side-tone level. In addition, AT command "AT+CLVL" is used to adjust the output gain level. For
more details, please refer to document [1] and document [5].
In order to improve audio performance, the following reference circuits are recommended. The audio signals have
to be layout according to differential signal layout rules as shown in following figures. If user needs to use an
amplifier circuit for audio, National Semiconductor Company's LM4890 is recommended.
3.7.1

Speaker Interface Configuration

Figure 18: Speaker reference circuit
Figure 19: Speaker with amplifier reference circuit
24
SIM900B_Hardware Design_V2.01 2012-05-07