ATF-38143-TR2 Avago Technologies US Inc., ATF-38143-TR2 Datasheet - Page 9

• Manufacturer Part Number: ATF-38143-TR2
• Description: TRANSISTOR,HEMT,N-CHAN,4.5V V(BR)DSS,90mA I(DSS),SOT-343R
• Manufacturer: Avago Technologies US Inc.

Specifications of ATF-38143-TR2

• Channel Type: N
• Configuration: Single Dual Source
• Gate-source Voltage (max): 4V
• Operating Temperature Classification: Military
• Mounting: Surface Mount
• Package Type: SOT-343
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Noise Parameter Applications Information
F
measurements while the F
extrapolated. The F
16 noise figure measurements made at 16 different
impedances using an ATN NP5 test system. From these
measurements, a true F
the true minimum noise figure of the device when the
device i s p resented w ith a n impedance m atching network
that transforms the source impedance, typically 50Ω, to
an impedance represented by the reflection coefficient
Γ
will present Γ
circuit losses. The noise figure of the completed amplifier
is equal to the noise figure of the device plus the losses
of the matching network preceding the device. The
noise figure of the device is equal to F
device is presented with Γ
of the matching network is other than Γ
figure of the device will be greater than F
following equation.
NF = F
Zo (|1 + Γ
9
min
o
. The designer must design a matching network that
values at 2 GHz and higher are based on
min
+ 4 R
o
to the device with minimal associated
n
|Γ
min
values are based on a set of
min
is calculated. F
s
o
o
mins
– Γ
|
. If the reflection coefficient
2
)(1 – Γ
below 2 GHz have been
o
|
2
s
|
2
)
min
o
min
, then the noise
only when the
min
based on the
represents
Where R
the optimum reflection coefficient required to produce
F
impedance actually presented to the device. The losses
of the matching networks are non-zero and they will
also add to the noise figure of the device creating a
higher amplifier noise figure. The losses of the matching
networks are related to the Q of the components and
associated printed circuit board loss. Γ
low at higher frequencies and increases as frequency is
lowered. Larger gate width devices will typically have a
lower Γ
Typically for FETs, the higher Γ
impedance much higher than 50Ω is required for the
device to produce F
lower L Band frequencies, the required impedance can be
in the vicinity of several thousand ohms. Matching to such
a high impedance requires very hi-Q components in order
to minimize circuit losses. As an example at 900 MHz,
when air-wound coils (Q > 100) are used for matching
networks, the loss can still be up to 0.25 dB which will add
directly to the noise figure of the device. Using muilti-layer
molded inductors with Qs in the 30 to 50 range results
in additional loss over the air-wound coil. Losses as high
as 0.5 dB or greater add to the typical 0.15 dB F
device creating an amplifier noise figure of nearly 0.65 dB.
A discussion concerning calculated and measured circuit
losses and their effect on amplifier noise figure is covered
in Avago Application 1085.
min
and Γ
o
as compared to narrower gate width devices.
n
/Z
s
is the reflection coefficient of the source
o
is the normalized noise resistance, Γ
min
. At VHF frequencies and even
o
usually infers that an
o
is typically fairly
min
of the
o
is