ATF521P8 Avago Technologies US Inc., ATF521P8 Datasheet - Page 18

• Manufacturer Part Number: ATF521P8
• Manufacturer: Avago Technologies US Inc.

Specifications of ATF521P8

• Configuration: Single Dual Source
• Drain-gate Voltage (max): -5 to 1V
• Operating Temperature (max): 150C
• Operating Temperature Classification: Military
• Mounting: Surface Mount
• Lead Free Status / Rohs Status: Compliant

Figure 13. ATF-521P8 Matching.
As described previously the input impedance must
be matched to S11* in order to guarantee return loss
greater than 10 dB. A high pass network is chosen for
this match. The output is matched to Γ
high pass network. The next step is to choose the
proper DC biasing conditions. From the data sheet,
ATF‑521P8 produces 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
I
V
V
V
V
Using equations 4, 5, 6, and 7, the biasing resistor values
are calculated in column 2 of table 1, and the actual
values used are listed in column 3.
RF
Figure 14. 2140 MHz Schematic.
18
R
dd
ds
g
be1
= 10 mA
in
= 0.62V
50 Ohm
= 4.5V
= 5 V
= 0.65 V
Match
Input
S11* = 0.89∠ -169
C1=1.2pF
C2=1.5nH
C3=4.7pF
C4=1µF
R4=61.9Ω
R2=383Ω
2PL
L2=12nH
R5=10Ω
L1=1.0nH
Γ
L
I
V
R
= 0.53∠ -176
g
Output
Match
I
50 Ohm
Q1
Q2
C2
ATF-521P8
2
R6=1.2Ω
2PL
V
V
be1 +
ds
R1=49.9Ω
R3=2.37Ω
7
C7=150pF
C6=.1µF
L3=39nH
L
C8=1.5pF
with another
C5=1µF
+5V
L4=3.9nH
RF
Table 1. Resistors for Active Bias.
Resistor
R1
R2
R3
R4
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
between the two bypass capacitors.
Performance of ATF-521P8 at 2140 MHz
ATF‑521P8 delivers excellent performance in the
WCDMA 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.
ou t
Calculated
50Ω
385Ω
2.38Ω
62Ω
Actual
49.9Ω
383Ω
2.37Ω
61.9Ω