Motorola A920 Service Manual page 62

A920: GSM PA
TX_VCO_LB
TX_VCO
TX_VCO_HB
AOC_DRIVE
N_BAND_0
MAGIC LV
DET_AOC
DET_REF
Description
U800 is a tri-band PA module that operates in EGSM, DCS and PCS bands. The nominal expected maximum gain is ~30dB. .
The AOC_DRIVE input from MAGIC_LV controls the PA output. The voltage applied at the pin is proportionally related to the output power of the PA, as the voltage
increases the gain or power level increases. N_BAND_0 is used to select the operating band. LV_EXC_EN will enable PA operation.
The power detector receives the amplified GSM signal at #1 (EGSM_IN), PCS and DCS at pin #12 (DCS_PCS_IN) from the U800. U810 is a dual combination direc-
tional coupler and temperature compensated power detector output. The power detector couples the Tx power input and feedbacks an output DET_AOC to MAGIC_LV.
A comparator within the MAGIC LV will sample DET_AOC and based on the power amplifier ramps will provide any necessary control voltage adjustments to
AOC_DRIVE The DET_REF is a reference voltage to MAGIC_LV. Expected nominal loss is <. 3dB.
PA_BATT+
U800
LV_EXC_EN
U810
DCS_PCS_TX
FL020
GSM_TX
RF
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