Fem With Integrated Power Amplifi Er Module; (Sky77531, U400); Only For Training And Service Purposes - LG GB220 Service Manual

3.3 FEM with integrated Power Amplifier Module (SKY77531, U400)
3.3.1 Internal Block Diagram
3.3.2 General Description
The SKY77531 is a transmit and receive front-end module (FEM) with Integrated Power Amplifier Control for
quad-band cellular handsets comprising GSM850/900 and DCS1800/PCS1900 operation. Designed in a low
profile, compact form factor.
The FEM also supports Class 12 General Packet Radio Service (GPRS) multi-slot operation.
The module consists of a GSM850/900 PA block and a DCS1800/PCS1900 PA block, impedance matching
circuitry for 50 Ω input and output impedances, TX harmonics filtering, high linearity and a low insertion
loss PHEMT RF switch, and a Power Amplifier Control (PAC) block with internal current sense resistor. A
custom BiCMOS integrated circuit provides the internal PAC function and decoder circuitry to control the RF
switches. The two Heterojunction Bipolar Transistor (HBT) PA blocks are fabricated onto a single Gallium
Arsenide (GaAs) die. One PA block supports the GSM850/900 bands and the other PA block supports the
DCS1800/PCS1900 bands. Both PA blocks share common power supply pads to distribute current. The
output of each PA block and the
Copyright © 2009 LG Electronics. Inc. All right reserved.

Only for training and service purposes

LGE Internal Use Only
Figure. 3-3-1 SKY77531 FUNCTIONAL BLOCK DIAGRAM
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Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3. TECHNICAL BRIEF
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