MRFIC1804R2 데이터 시트보기 (PDF) - Motorola => Freescale
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MRFIC1804R2 Datasheet PDF : 6 Pages
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DESIGN AND APPLICATIONS INFORMATION
The MRFIC1804 consists of a two–stage GaAs MESFET
low noise amplifier and a single ended MESFET mixer. The
LNA design conserves bias current through stacking of the
two FETs, thus reusing the current. The mixer consists of a
common gate stage driving a common source stage with
the IF output being the drain of the common source stage
shunted with 15 pF. The LNA output and mixer input have
been separated to allow the addition of an external image
filter. Such a filter, usually ceramic, is useful in improving
the mixer noise figure and third order intercept perfor-
mance. It also provides LO rejection to reduce the amount
of LO power which may leak to the antenna. Alternatively,
image trapping can be implemented at the LNA input or out-
put with discrete or distributed components.
The design has been optimized for application in the PCS
bands around 1.9 GHz but is usable from around 1.5 GHz to
2.2 GHz. For applications at 1.9 GHz and IFs of 110 MHz or
240 MHz, the circuit shown in Figure 1 can be used. This
circuit was used to derive the characterization data shown
in Figures 3 through 8. For other IF frequencies in the 100
MHz to 350 MHz range, use the IF equivalent circuit shown
in Figure 2 for matching network design. As can be seen in
the characterization curves, performance appears to de-
grade above about 1.85 GHz. This is partially a function of
the circuit shown in Figure 1 and can be improved, first, by
adjusting the LO input match, second, by matching LNA in-
put and and the mixer input off chip.
As with all RF circuits, layout is important. Ground vias
must be close to the component or lead to be grounded and
vias must be plentiful. RF signal lines should be controlled
impedance such as microstrip. Bypassing of power supply
leads as shown in Figure 1 is essential to avoid oscillation of
the circuits.
EVALUATION BOARDS
Evaluation boards are available for RF Monolithic Inte-
grated Circuits by adding a “TF” suffix to the device type.
For a complete list of currently available boards and ones
in development for newly introduced poduct, please con-
tact your local Motorola Distributor or Sales Office.
MOTOROLA RF DEVICE DATA
MRFIC1804
5
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