MC13821 Datasheet, PDF (10/42 Pages) Freescale Semiconductor, Inc – Low Noise Amplifier with Bypass Switch

Application Information
Input 3rd Order Intercept Point vs. Icc
2140 MHz Application Circuit
6
5
4
3
2
1
0
-1
-2
1
2
3
4
5
Icc (mA)
Figure 8. Input 3rd Order Intercept Point vs. Icc for the 2140 MHz Application Circuit
(Rbias varied from 1.2 kΩ to 3 kΩ)
3 Application Information
The MC13821 SiGe:C LNA is designed for applications in the 1000 MHz to 2.4 GHz range. It has three
different modes: High Gain, Low Gain (Bypass) and Disabled. The IC is programmable through the Gain
and Enable pins. The logic truth table is given in Table 5.
In these application examples a balance is made between the competing RF performance characteristics of
I_CC, NF, gain, IP3 and return losses with unconditional stability. Conjugate matching is not used for the
input or output. Instead, matching which achieves a trade-off in RF performance qualities is utilized. For
a particular application or spec requirement, the matching can be changed to achieve enhanced
performance of one parameter at the expense of other parameters.
Application information for 1575, 1960, 2140 and 2400 MHz are shown. For each application, two current
drain examples are provided. Typical RF performance is shown for two values of bias resistor R1: 1.2 kΩ
and 2 kΩ, see Table 6, Table 7, Table 8, and Table 9. These two current drain states offer variation in
intercept point, gain, and noise figure. For 1960 and 2140 MHz, additional application circuits are shown.
These demonstrate specific performance characteristics and utilize varying input and output matches and
different biasing resistors.
Measurements are made at a bias of V_CC = 2.75 V. Freq. spacing for IP3 measurements is 200 kHz.
Non-linear measurements are made at Pin = -30 dB. The board loss corrections for these boards are: Input
0.16 dB, Output 0.2 dB. Gain and NF results incorporate these corrections in order to better reflect the
actual performance of the device.
3.1 1575 MHz Application
This application circuit was designed to provide NF < 1.2 dB, S21 gain > 18 dB, OIP3 of 18 dBm with
S11 better than -10 dB and S22 better than -10 dB at 1575 MHz with unconditional stability from 100 MHz
to 10 GHz. Typical performance that can be expected from this circuit at 2.75 V V_CC is listed in Table 6.
MC13821 Advance Information, Rev. 1.0
10
Freescale Semiconductor