ATF-521P8 View Datasheet(PDF) - HP => Agilent Technologies
Part Name
Description
MFG CO.
ATF-521P8
HP => Agilent Technologies
'ATF-521P8' PDF : 24 Pages View PDF
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
ΓL with another 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
IR = 10 mA
Vdd = 5 V
Vds = 4.5 V
Vg = 0.62 V
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 values 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 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.
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.
20
Gain
15
10
5
NF
0
1.6
1.8
2.0
2.2 2.4
2.6
FREQUENCY (GHz)
Figure 15. Gain and Noise Figure vs. Frequency.
Input and output return loss are
both greater that 10 dB. Although
somewhat narrowband, the
response is adequate in the
frequency range of 2110 MHz to
2170 MHz for the WCDMA
downlink. If wider band response
is need, using a balanced configu-
ration improves return loss and
doubles OIP3.
0
S11
-5
-10
S22
-15
1.6
1.8
2.0
2.2
2.4
2.6
FREQUENCY (GHz)
Figure 16. Input and Output Return Loss vs.
Frequency.
Perhaps the most critical system
level specification for the
ATF-521P8 lies in its distortion-
less output power. Typically,
amplifiers are characterized for
linearity by measuring OIP3. This
is a two-tone harmonic measure-
ment using CW signals. But
because WCDMA is a modulated
waveform spread across
3.84 MHz, it is difficult to corre-
lated good OIP3 to good ACLR.
Thus, both are measured and
presented to avoid ambiguity.
18
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