TQ5635 Ver la hoja de datos (PDF) - TriQuint Semiconductor
Número de pieza
componentes Descripción
Fabricante
TQ5635 Datasheet PDF : 25 Pages
| |||
TQ5635
Data Sheet
For most applications needing maximum LNA gain, it
will probably be sufficient to simply ground pins 15
and 16 as shown in the second diagram in Figure 9.
However, in some cases a small amount of
inductance may be needed from pins 15 and 16 to
ground in order to lower the LNA gain. Because of
stray inductance on the application board layout, it is
difficult to give a precise value of L as a function of
gain reduction. The first diagram in Figure 9
illustrates one way of doing this. A short is placed
across the inductor until the needed gain is arrived at.
2. Determine the LNA Matching Network
Matching network design for the TQ5635 LNA is much
simpler than designing with discrete transistors. The
TQ5635 LNA was designed so that the optimum noise
match is very close to the conjugate match. Thus
once a match to 50ohms is attained, only a slight
adjustment to the L and C values may be needed for
optimum noise figure. If the design uses 5-8mil
dielectric FR4 board, then it is likely that the
component values on the evaluation board can be
used for a starting point. Alternately, a network can
be synthesized from the S-parameter values at the
end of this note.
3. LO Buffer Tuning
The drain of the LO buffer is brought out to pin 10
where it is fed DC bias via an inductor. The inductor
resonates with the internal and external parasitic
capacitance associated with that pin. For maximum
performance the resonance must be at or near the
desired LO frequency. Figure 10 shows a properly
tuned LO buffer. Notice that the LO frequency range
of interest is to the left of the peak. We recommend
that the LO is tuned slightly higher in frequency, so
that the desired band is on the lower, more gradual
side of the slope. Thus there is less change in
performance versus frequency. We have also found
empirically that tuning the LO slightly higher in
frequency results in much better LO input and RF
input matches.
GND
RF In
GND
LNA
Bias
TQ5635
MXR
In
GND
V
DD
LO
In
GND
RF In
GND
LNA
Bias
TQ5635
MXR
In
GND
V
DD
LO
In
For Lower Gain: add a
small inductance to pins
15 and 16
Recommended: Ground
pins 15 and 16 for
maximum gain
Figure 9: LNA Source Inductor Realization
16
For additional information and latest specifications, see our website: www.triquint.com
Share Link: 