ATF-521P8-BLK View Datasheet(PDF) - Avago Technologies
Part Name
Description
MFG CO.
ATF-521P8-BLK
Avago Technologies
'ATF-521P8-BLK' PDF : 23 Pages View PDF
Input
Match
50 Ohm
2PL
Output
Match
50 Ohm
S11* = 0.89∠ -169 ΓL = 0.53∠ -176
Figure 13. ATF-521P8 Matching.
As described previously the input impedance must be
matched to S11* in order to guarantee return loss great‑
er than 10 dB. A high pass network is chosen for this
match. The output is matched to ΓL with another high
pass network. The next step is to choose the proper DC
biasing conditions. From the data sheet, ATF-521P8 pro‑
duces good linearity at a drain current of 200mA and
a drain to source voltage of 4.5V. Thus to construct the
active bias circuit described, the following parameters
are given:
Ids = 200 mA
IR = 10 mA
Vdd = 5 V
Vds = 4.5V
Vg = 0.62V
Vbe1 = 0.65 V
Using equations 4, 5, 6, and 7, the biasing resistor values
are calculated in column 2 of table 1, and the actual val‑
ues used are listed in column 3.
Resistor Calculated Actual
R1
50Ω
49.9Ω
R2
385Ω
383Ω
R3
2.38Ω
2.37Ω
R4
62Ω
61.9Ω
Table 1. Resistors for Active Bias.
The entire circuit schematic for a 2.14 GHz Tx driver
amplifier is shown below in Figure 14. Capacitors C4,
C5, and C6 are added as a low frequency bypass. These
terminate second order harmonics and help improve
linearity. Resistors R5 and R6 also help terminate low
frequencies, and can prevent resonant frequencies be‑
tween the two bypass capacitors.
Performance of ATF-521P8 at 2140 MHz
ATF-521P8 delivers excellent performance in the WCD‑
MA frequency band. With a drain-to-source voltage of
4.5V and a drain current of 200 mA, this device has 16.5
dB of gain and 1.55 dB of noise figure as show in Figure
15.
IR
R2=383Ω
Vg
R4=61.9Ω
C4=1µF
R1=49.9Ω
Q1
Vbe1+
+5V
C5=1µF
Vds
Q2
R3=2.37Ω
IC2
C6=.1µF
C3=4.7pF R5=10Ω
R6=1.2Ω
C7=150pF
L2=12nH
L3=39nH
RFin
C1=1.2pF
L1=1.0nH 2 2PL 7
C8=1.5pF
RFout
C2=1.5nH
ATF-521P8
L4=3.9nH
Figure 14. 2140 MHz Schematic.
18
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