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The signals 3V_P_TX and 3V_G_TX are controls supplies used to enable the two
power control op-amps IC105 and IC108.
The output from the P.A follows the TX path, which uses the control supplies:-
GSM_PRE_ON or PCN_PRE_ON to enable the TX switching diodes D400/D401.
The RF signal then passes through the diplexor and onto the antenna.
The diplexor is tuned to the GSM or PCN duplex spacing so enabling selectivity
between GSM and PCN Rx or Tx.
Fixed Control Loop
Stripline
VBAT-
R144
VBAT_PCN
Fig. 9. The PA Control Circuit
V_CONT
GND
IC109
4
VBAT
3
R136
V_CONT
TR108
GND
TR110
3
4
2
1
GND
TR109
-
1
+
2
V_CONT
V_CONT
D101
V_ERROR
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