Neo_M660A GPRS Module Hardware User Guide
Copyright © Neoway Technology Co., Ltd
24
Figure 3-23
Reference design for common audio input
GPRS Module
33 pF
33 pF
MICN
MICP
MIC_BIAS
Baseband
Circuit
2.2 uF
R6
2.2 KΩ
R5
2.2 kΩ
C1
C2
User's
Circuit
R1
R3
R2
R4
In Figure 3-22 and Figure 3-23, the audio input circuits are designed to meet the requirements for small
audio signal, far away from interference source and masking PCB routing by ground.
Figure 3-24 shows a reference design for the receiver interface, which can drive a 32 Ω receiver directly.
Figure 3-24
Reference design for receiver output
GPRS Module
33 pF
Receiver@32Ω
33 pF
100 pF
RECN
RECP
If an external amplifier is used for driving the speakers, coupling capacitors of 2.2 μF to 4.7 μF should be
used to block the DC voltage, as shown in Figure 3-25
.