Siemens SXG 75 - Page 13

Release 1.0
Technical Documentation 01/2006
TD_Repair_L3_SXG75_R1.0.pdf Page 13 of 73
5.3.3
GSM power amplifier
The output signals (OUT1 and OUT2) from the GSM TX VCO are led to the power amplifier.
The power amplifier is the PA-module N300. It contains of two separate amplifier chains for
GSM900 and GSM1800/GSM1900 operation. The amplification is controlled with the signal
VRAMP. The appropriate amplifier chain is activated by the logic signal GSM_PA__BAND
which is provided by the MSM6250. The N300 is activated through the signal VTXB, which
is the level shifted GSM_PA_EN provided by the MSM6250.
The voltage VBATT is provided by the battery.
VBATT
to antenna
switch
GSM_PA_EN
(level shifted)
PA RAMP
OUT2 from TX VCO
OUT1 from TX VCO
GSM_PA_BAND
Circuit diagram (sheet 3)
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