RF6886 Datasheet, PDF (5/16 Pages) RF Micro Devices – 3.6V, 100MHz TO 1000MHz LINEAR POWER AMPLIFIER

RF6886
Theory of Operation
This section provides specific guidelines for operation of RF6886.
Applications can generally be placed into two categories:
1. High power applications
• Output power ranging between 34.5 - 36.5dBm
• Efficiency >50% in band of interest
2. Linear applications
• RF6886 shows linearity along the lines of a handset power amplifier in terms of adjacent channel power (ACP)
performance, with the distinct advantage of obtaining ACP compliance at >2x comparative output power. Resultant
output power for linear operation will depend on the waveform being considered.
All pertinent specifications and performance curves are seen in the tabular and graph sections of the data sheet. The first
standard evaluation board has been matched for 865MHz to 955MHz. Operation with V_CC=3.6V shows output power >36dBm
and efficiency >50%. For reduced power ranges, efficiency is maintained, with no change to output match, by lowering V_CC. See
data for 3.3/3.0V in the tables provided. The standard evaluation board also demonstrates impressive linearity, shown with
conventional CDMA modulation.
The same data set format is also provided for the 433MHz to 470MHz evaluation board. Nominal data is taken with V_CC=3.6V
and V_REG1/2=3.1V. For linear operation, it has been shown that reducing V_REG1/2 to 2.7 - 2.8V enhances performance. This
can be explained by observing how the compression characteristic behaves. Operation with VREG=3.1V shows gradual (soft)
compression once power exceeds 31dBm. With VREG reduced to 2.7 - 2.8V, small signal gain drops by 1 - 2dB. Self bias is now
more prominent at 31dBm, and gain expansion offsets slow compression. The result is flattening of the gain characteristic,
extending effective compression point out in power. Waveform distortion is reduced as compared to the VREG=3.1V case, and
adjacent channel power improves. The sole advantage in using VREG=3.1V would be a slightly higher value for saturated out-
put power.
Low thermal resistance enables reliable high power operation, provided that output load is set to achieve efficiency equal to or
better than that seen on the RFMD evaluation boards.
The maximum rating for output load VSWR on page 2 calls out requirement for discussion in this section. RF6886 has shown
excellent performance into 50, but any system using it as a final amplifier will have to take VSWR variation into account. Test
on properly matched evaluation board has shown that rated output power is obtained with 10dBm at RF input. Practically
speaking then, at or near 10dBm would be a maximum reasonable limit for input power. When considering VSWR variation,
ruggedness is one of the main considerations. Ruggedness here, being the worse case VSWR which can be tolerated for a tran-
sient period without damage to the device. The following maximum VSWR limits apply:
V_CC
Freq
V
MHz
3.6
865 to 955
3.3
3
3.6
433 to 470
3.3
3
P_OUT into 50 Load
(Across Band)
dBm
36.2 to 35.2
35.5 to 34.4
34.4 to 33.4
37 to 36.4
36.3 to 35.6
35.2 to 34.5
Maximum Practical
Input Drive
dBm
10
10
8
10
10
8
Maximum Output VSWR
(Survival)
3.5:1
5.0:1
5.0:1
3.5:1
5.0:1
5.0:1
DS100817
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at ([phone] or [e-mail].
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