TQ5131 Ver la hoja de datos (PDF) - TriQuint Semiconductor
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TQ5131 Datasheet PDF : 14 Pages
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TQ5131
Data Sheet
recommends placing the image-reject filter as close to the IC as
possible. In TriQuint’s demo board its position is 42 mils from
the pad of the matching inductor and 126 mils from the IC pad.
This location for the image-reject filter works well.
CDMA IF Amplifier
The CDMA IF amplifier is an open drain stage with a gain step
to adjust the output power levels according to the system
requirement. The source of the CDMA IF amplifier is connected
directly to pin 3. This allows the system designer to adjust gain,
output intercept and current (GIC) by adding an external self-
bias circuit at this pin (see figure 4a and b). Recommended
capacitor value in the self-bias circuit is 0.022 uF or greater. In
addition to the 0.5 to 1 dB more of input intercept obtained by
using a large value capacitor, the effects of low frequency
components present at this pin are also reduced.
Figure 4a. GIC Pin Self-Bias Circuit
TQ5131
1
8
2
7
R2
3
6
R3
C4 4
5
C4 = 0.022uF
R2 = 8.2 Ω
R3 = 82 Ω
Note: These values were optimized for TriQuint's 5131 Demo
board. The discrepancy between these values and those of the
customer's application may differ due to board and component
parasitics.
Performance Vs. Bias Resistance (R3) for CDMA
High Gain: (RF_Freq=882MHz, IF_Freq=85MHz,
LO_Freq=967MHz, PLO=-4dBm, Vdd=2.8)
17
12
7
Gain (dB)
Idd (mA)
2
IIP3 (dBm)
-3
82 100 130 160 180 200 220 240 270 300
Bias Resistance R3 (ohms): (R2 constant at 8.2 ohms)
Figure 4b. Performance Vs. GIC Pin Bias Resistance, R3
AC degeneration of the CDMA IFA source has minimum or no
effect on AMPS performance. Maximum gain is obtained when
the total DC resistance (R2 + R3) at pin 3 is bypassed (see
figure 4c).
Performance Vs. Bias Resistance (R2) for CDMA
High Gain: (RF_Freq=882MHz, IF_Freq=85MHz,
LO_Freeq=967MHz, PLO=-4dBm, Vdd=2.8)
18
16
14
12
10
Gain (dB)
8
IIP3 (dBm)
6
Idd (mA)
4
2
0
0
10 20 30 39 51 62
Bias Resistance R2 (ohms): (R3 constant at 82 ohms)
Figure 4c. Performance Vs. GIC Pin Bias Resistance, R2
Once the operating point is chosen, the designer still has
flexibility to adjust gain and intercept by varying the ratio of the
total bias resistance, R2 + R3. In figure 4d one can observe how
gain and intercept change while the current remains
approximately constant at 16mA.
8
For additional information and latest specifications, see our website: www.triquint.com
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