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參數(shù)資料
| 型號： | ATF-35143-TR2G |
| 元件分類： | 小信號晶體管 |
| 英文描述： | L BAND, Si, N-CHANNEL, RF SMALL SIGNAL, HEMFET |
| 封裝： | LEAD FREE, PLASTIC, SC-70, 4 PIN |
| 文件頁數(shù)： | 7/19頁 |
| 文件大?。?/td> | 608K |
| 代理商： | ATF-35143-TR2G |
15
Noise Parameter Applications Information
Fmin values at 2 GHz and higher are based on
measurements while the Fmins below 2 GHz have been
extrapolated. The Fmin values are based on a set of
16 noise figure measurements made at 16 different
impedances using an ATN NP5 test system. From these
measurements, a true Fmin is calculated. Fmin represents
the true minimum noise figure of the device when the
deviceispresentedwithanimpedancematchingnetwork
that transforms the source impedance, typically 50Ω, to
an impedance represented by the reflection coefficient
Γo. The designer must design a matching network that
will present Γo to the device with minimal associated
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 Fmin only when the
device is presented with Γo. If the reflection coefficient
of the matching network is other than Γo, then the noise
figure of the device will be greater than Fmin based on the
following equation.
NF = Fmin + 4 Rn
|Γs – Γo | 2
Zo
(|1 + Γo|2)(1- Γs|2)
Where Rn/Zo is the normalized noise resistance, Γo is
the optimum reflection coefficient required to produce
Fmin and Γs is the reflection coefficient of the source
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. Γo is typically fairly
low at higher frequencies and increases as frequency is
lowered. Larger gate width devices will typically have a
lower Γo as compared to narrower gate width devices.
Typically for FETs, the higher Γo usually infers that an
impedance much higher than 50Ω is required for the
device to produce Fmin. At VHF frequencies and even
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 airwwound 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 muiltilayer molded inductors with Qs in the 30 to
50 range results in additional loss over the airwound coil.
Losses as high as 0.5 dB or greater add to the typical 0.15
dB Fmin of the 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.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| ATF-35143-TR1 | X BAND, Si, N-CHANNEL, RF SMALL SIGNAL, HEMFET |
| ATF-35143-BLK | X BAND, Si, N-CHANNEL, RF SMALL SIGNAL, HEMFET |
| ATF-35143-TR2 | X BAND, Si, N-CHANNEL, RF SMALL SIGNAL, HEMFET |
| ATF-35143-TR2 | X BAND, Si, N-CHANNEL, RF SMALL SIGNAL, HEMFET |
| ATF-35143-TR1 | X BAND, Si, N-CHANNEL, RF SMALL SIGNAL, HEMFET |
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| ATF35576 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:TRANSISTOR | JFET | N-CHANNEL | 20MA I(DSS) | MICRO-XVAR |
| ATF36077 | 制造商:AGILENT 制造商全稱:AGILENT 功能描述:2-18 GHz Ultra Low Noise Pseudomorphic HEMT |
| ATF-36077 | 制造商:AGILENT 制造商全稱:AGILENT 功能描述:2-18 GHz Ultra Low Noise Pseudomorphic HEMT |
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