Telit Wireless Solutions GE910 - Page 55

GE910 Hardware User Guide
1vv0300962 Rev.12 2013-10-22
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved
page 55 of 83
Mod. 0805 2011-07 Rev.2
If a "balanced way" is anyway desired, much more care has to be taken to Vmic noise and
ground noise; also the 33pF-100Ohm-33pF -RF filter has to be doubled (one each wire).
100n
1K
1K
100
33pF 33pF
100n
100
33pF 33pF
1K
1u
MIC+
MIC-
GND
Vmic
÷10K
2÷5v
÷10u
TELIT MODULE
-
+
INPUTADC
TIP: Since the J-FET transistor inside the microphone acts as RF detector amplifier, ask vendor
for a microphone with anti-EMI capacitor (usually a 33pF or a 10pF capacitor placed across the
output terminals inside the case).
100n
100n
1K
2.2K
1u
100
33pF 33pF
÷10u
Vmic
MIC+
MIC-
GND
÷10K
2÷5v
TELIT MODULE
-
+
INPUTADC
+
-