
Applications Information
Figure 6 shows the Icc current drain for a range of values for the external bias resistor Rbias.
6.5
6
5.5
5
4.5
4
3.5
3
2.5
2
y ? = ? 1.7619x 2 ‐ 8.5883x ? + ? 13.293
R2 ? = ? 0.9983
Icc ? mA
Poly. ? (Icc ? mA)
1.1
1.3
1.5
1.7
1.9
2.1
Rbias ? value ? (kohm)
Figure 6. Icc vs. Bias Resistor R1 Value
3
Applications Information
The MC13852 LNA is designed for applications in the 400 MHz to 1 GHz range. It has three different
modes: High Gain, Low Gain (bypass) and Standby. The LNA is programmable through the Gain and
Enable pins. The logic truth table is given in Table 3 . The internal bypass switch is designed for broadband
applications.
One of the advantages of the MC13852 is the simplification of the matching network in both bypass and
amplifier modes. The bypass switch is designed so that changes of input and output return losses between
bypass mode and active mode are minimized and the matching network design is simplified.
In these application examples, a balance is made between the competing RF performance characteristics
of Icc, 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 used. For a
particular application or specification requirement, the matching can be changed to achieve enhanced
performance of one parameter.
Measurements are made at a bias of Vcc = 2.75 V. Frequency spacing for IP3 measurements is 200 kHz.
Non-linear measurements are made at Pin = -30 dBm. Typical application circuits are provided for
434 MHz and 900 MHz applications. Typical RF performance is shown for two values of bias resistor R1:
1.2 k Ω and 1.5 k Ω . These two current drain levels offer variations in intercept point, gain and noise figure.
Included with each application are the schematics and electrical performance.
8
?
?
Section 4 provides the evaluation board layout and Bill of Material for the circuits.
Section 5 provides Smith charts with gain and noise circles for each application frequency.
MC13852 Advance Information, Rev. 2.0
Freescale Semiconductor