RF Front End
MC13192EVB Reference Manual, Rev. 1.2
3-6
Freescale Semiconductor
3.5
LNA Bias Circuits
Figure 3-7. Basic LNA Bias Circuit Schematic
The default LNA bias runs through R112 with a nominal bias of 3.75 mA. Some variation in bias is to be
expected with this simple circuit, but this is acceptable in many applications. The bias is expected to be
within the range of 2.4 - 4.8 mA, which gives a few dB's of gain variation. For measurement convenience,
the LNA is on at all times. Switching the base feed to GPIO1 turns the LNA off in standby and sleep mode.
This is done by removing R112 and adding R119. Because the GPIO1 does not work properly in some test
modes, the default configuration is with R112 mounted. In applications operating over a range of supply
voltages and extended temperature ranges, a more sophisticated bias arrangement is needed. Also, in
battery applications, the LNA should only be turned on when necessary.
Q101
MBC13900
2
4
1,
3
C128
10pF
Input, 50 Ohm
L104
5.6nH
C132
100pF
L105
1.5nH
R140
220R
Output, 50 Ohm
C105
1.0pF
C115
10pF
R108
150R
R112
100K
3V0_LNA
R119
100K
Not Mounted
GPIO1
Summary of Contents for FREESCALE MC13192
Page 1: ...Document Number MC13192EVBRM Rev 1 2 09 2006 MC13192 Evaluation Board Reference Manual...
Page 8: ...MC13192EVB Reference Manual Rev 1 2 vi Freescale Semiconductor...
Page 10: ...Safety Information MC13192EVB Reference Manual Rev 1 2 1 2 Freescale Semiconductor...
Page 18: ...System Overview MC13192EVB Reference Manual Rev 1 2 2 8 Freescale Semiconductor...
Page 32: ...RF Front End MC13192EVB Reference Manual Rev 1 2 3 14 Freescale Semiconductor...
Page 34: ...PCB and MC13192EVB Interfaces MC13192EVB Reference Manual Rev 1 2 4 2 Freescale Semiconductor...