FLY SP-770, Как в инструкции

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4. POWER AMPLIFIER FOR GSM850 / DCS1800 / PCS1900
4.1 Block Diagram and Description
The SKY77328 Power Amplifier Module (PAM) is designed in a low profile (1.2 mm),
compact form factor for quad-band cellular handsets comprising GSM850, DCS1800, and
PCS1900 operation. The PAM also supports Class 12 General Packet Radio Service (GPRS)
multi-slot operation.
The module consists of separate GSM850 PA and DCS1800/PCS1900 PA blocks,
impedance-matching circuitry for 50 Ω input and output impedances, and a Power
Amplifier Control (PAC) block with an internal current-sense resistor. The custom BiCMOS
integrated circuit provides the internal PAC function and interface circuitry. Fabricated
onto a single Gallium Arsenide (GaAs) die, one Heterojunction Bipolar Transistor (HBT) PA
block supports the GSM850 bands and the other supports the DCS1800 and PCS1900 bands.
Both PA blocks share common power supply pins to distribute current. The GaAs die, the
Silicon (Si) die, and the passive components are mounted on a multi-layer laminate
substrate. The assembly is encapsulated with plastic overmold.
RF input and output ports of the SKY77328 are internally matched to a 50 Ω load to reduce
the number of external components for a quad-band design. Extremely low leakage current
(2.5 µA, typical) of the dual PA module maximizes handset standby time. The SKY77328
also contains band-select switching circuitry to select GSM (logic 0) or DCS/PCS (logic 1)
as determined from the Band Select (BS) signal. In Figure 1 below, the BS pin selects the
PA output (DCS/PCS OUT or GSM850 OUT) and the Analog Power Control (VAPC) controls