SA5204A Datasheet, PDF (8/13 Pages) NXP Semiconductors – Wide-band high-frequency amplifier

Philips Semiconductors
Wide-band high-frequency amplifier
Product specification
SA5204A
PC BOARD MOUNTING
In order to realize satisfactory mounting of the SA5204A to a PC
board, certain techniques need to be utilized. The board must be
double-sided with copper and all pins must be soldered to their
respective areas (i.e., all GND and V_CC pins on the package). The
power supply should be decoupled with a capacitor as close to the
V_CC pins as possible, and an RF choke should be inserted between
the supply and the device. Caution should be exercised in the
connection of input and output pins. Standard microstrip should be
observed wherever possible. There should be no solder bumps or
burrs or any obstructions in the signal path to cause launching
problems. The path should be as straight as possible and lead
lengths as short as possible from the part to the cable connection.
Another important consideration is that the input and output should
be AC-coupled. This is because at V_CC=6V, the input is
approximately at 1V while the output is at 3.1V. The output must be
decoupled into a low-impedance system, or the DC bias on the
output of the amplifier will be loaded down, causing loss of output
power. The easiest way to decouple the entire amplifier is by
soldering a high-frequency chip capacitor directly to the input and
output pins of the device. This circuit is shown in Figure 18. Follow
these recommendations to get the best frequency response and
noise immunity. The board design is as important as the integrated
circuit design itself.
SCATTERING PARAMETERS
The primary specifications for the SA5204A are listed as
S-parameters. S-parameters are measurements of incident and
reflected currents and voltages between the source, amplifier, and
load as well as transmission losses. The parameters for a two-port
network are defined in Figure 19.
V_CC
RF CHOKE
DECOUPLING
CAPACITOR
V_IN
AC
COUPLING
CAPACITOR
5204A
V_OUT
AC
COUPLING
CAPACITOR
Figure 18. Circuit Schematic for
Coupling and Power Supply Decoupling
SR00210
Actual S-parameter measurements using an HP network analyzer
(model 8505A) and an HP S-parameter tester (models 8503A/B) are
shown in Figure 20.
Values for the figures below are measured and specified in the data
sheet to ease adaptation and comparison of the SA5204A to other
high-frequency amplifiers.
The most important parameter is S₂₁. It is defined as the square root
of the power gain, and, in decibels, is equal to voltage gain as
shown below:
Z_D=Z_IN=Z_OUT for the SA5204A
P_IN
)
V_IN2
Z_D
SA5204A
Z_D
P_OUT
)
V_OUT2
Z_D
N
P_OUT
P_IN
V_OUT2
+
Z_D
V_IN2
+
V_OUT2
V_IN2
+ P_I
Z_D
P_I=V_I ²
P_I=Insertion Power Gain
V_I=Insertion Voltage Gain
Measured value for the
SA5204A = |S₂₁ | ² = 100
NP_I
+
P_OUT
P_IN
+ | S₂₁ | ²
+ 100
and V_I
+
V_OUT
V_IN
+ ^ǸP_I
+ S₂₁ + 10
In decibels:
P_I(dB) =10 Log | S₂₁ | ² = 20dB
V_I(dB) = 20 Log S₂₁ = 20dB
∴ P_I(dB) = V_I(dB) = S_21(dB) = 20dB
Also measured on the same system are the respective voltage
standing wave ratios. These are shown in Figure 21. The VSWR
can be seen to be below 1.5 across the entire operational frequency
range.
Relationships exist between the input and output return losses and
the voltage standing wave ratios. These relationships are as follows:
1997 Nov 07
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