ADL5521ACPZ-WP AD [Analog Devices], ADL5521ACPZ-WP Datasheet - Page 38

• Manufacturer Part Number: ADL5521ACPZ-WP
• Description: 400 MHz - 4000 MHz Low Noise Amplifier
• Manufacturer: AD [Analog Devices]

ADL5521
S11 Parameters of ADL5521,23 with S22 Matched
To determine the correct matching circuit for optimal noise, the
next step is to look at the results of S11 for the various frequencies
at which S22 was tuned earlier in this note. Once the S11 is
determined for a particular frequency, all that needs to be done is
to find the matching components that provide that match.
Figure 127 to Figure 132 show S11 for the various frequencies.
Again, these measurements are all based on S22 being matched at
that particular frequency.
Note that the S11 for every example shown in Figure 127 to Figure
132 is either in the lower left quadrant of the Smith Chart or
slightly into the upper left. To move this impedance in the given
noise circle first requires a series L component at the LNA input.
The values for L in all of the examples will differ, but a correct
value of L will move the match along the constant R circle up into
upper left quadrant of the Smith Chart.
A shunt capacitor can then be added to move the match along a
constant admittance line, down and to the right, hopefully right
into the center of the noise circle given in Figure 126.
The solution for the structure of the match for all of the examples
in Figure 127 to Figure 132 is a series L to the input of the LNA,
and a shunt capacitor at the generator end of this inductor.
An example of the effect of the series L, shunt C match, based on
the 800MHz example, is given in Figure 133. This example uses
the output from the Agilent ADS Smith Chart tool.
Figure 126. Area of Optimal Noise Matching for ADL5521, 23
Rev. PrC| Page 38 of 45
Frequency
1400 MHz
1950 MHz
2150 MHz
2400 MHz
900 MHz
500MHz
750MHz
Table 8. L and C Values for ADL5521 Matching Circuits at Various Frequencies
2.4pF
2.4pF
1.3pF
2.0pf
1.3pf
1.3pf
C1
na
Preliminary Technical Data
82pf
C2
1nF
C3
na
1nf
C5
8.2nH
5.1nH
1.1nH
1.1nH
1.3nH
11nH
9nH
L1
3.4nH
3.4nH
12nH
0 Ω
0 Ω
0 Ω
0 Ω
L2