MRF89XAM8A-I Datasheet, PDF (96/140 Pages) Microchip Technology – Ultra Low-Power, Integrated ISM Band Sub-GHz Transceiver

MRF89XA
4.4 POWER AMPLIFIER
The Power Amplifier (PA) integrated in the MRF89XA
operates under a regulated voltage supply of 1.8V. The
external RF choke inductor is biased by an internal reg-
ulator output made available on the PARS pin (pin 29).
These features help PA output power to be consistent
over the power supply range. This is important for
applications that allow predictable RF performance and
battery life.
4.4.1 OPTIMUM LOAD IMPEDANCE
As the PA and the LNA front-ends in the MRF89XA
share the same input/output pin, they are internally
matched to approximately 50Ω. Figure 4-4 illustrates
optimum load impedance of RFIO through an imped-
ance chart.
FIGURE 4-4:
OPTIMAL LOAD IMPEDANCE CHART
Pmax-1dB circle
Max Power
Zopt = 30 + j25Ω
Note: Refer to Section 4.7, Bill of Materials for
an optimized PA load setting.
DS70622C-page 96
Preliminary
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