1.6GHz TWO STAGE CMOS LOW NOISE AMPLIFIER

 XC2404 SERIES

1.5mm x 1.5mm x 0.6mm USP-8A01 PACKAGE

Low Noise, High Gain Solution

The XC2404 series is an ultra-low-noise amplifier (LNA) with low operating voltage, low noise & low power consumption. The key parameter with any LNA is the Noise Figure, represented in Decibels. RF design engineers are ideally looking for a solution that offers the lowest possible noise figure with a preference for 1.0dB and below at the RF Frequency of 1.6GHz. The XC2404’s noise figure is 0.94dB at that frequency level making it ideally suited for use with noise sensitive GPS applications.

However, the noise figure of the LNA is only as relevant as the gain that the LNA can achieve at the same time. This is because the LNA comes early in the transmission chain so it needs to amplify the weak signal received as much as possible, whilst at the same time, keeping the noise figure as low as possible ! Generally, a gain of between 15~20dB is required. The XC2404’s Gain is 26.5dB, so combining this with the low noise figure of 0.94dB, the XC2404 really does add up to a winning solution.

Fig.1 : Gain – RF Figure
 

Fixed Bias vs Self Bias

The XC2404’s operating voltage range is 1.14V~1.26V (1.2V typ.) when operating in Fixed Bias mode but for applications that only have higher power supply rails such as 1.8V or 2.85V, the XC2404 can also be used in a Self Bias mode by attaching an external Rbias resistor on the input side to give added flexibility. This also means that an additional LDO, that would have been required to regulate down from 1.8V or 2.85V to the required 1.2V, is no longer required.

The two application circuits are shown below :

Fig. 2 : Typical Circuit Diagram for Fixed Bias & Self Bias Operation
 

CMOS Process

In addition to the low noise figure and the high gain, what also makes the XC2404 stand out is the very low power consumption of only 12mW (fixed bias mode). Unlike other LNAs, which mainly use either GaAs, SiGe or SiGe BiCMOS processes, the XC2404 has been developed using a 0.13µ CMOS process which results in the extremely low power consumption figure.
 

Ultra Small Solution

The XC2404 is available in an ultra low profile USP-8A01 package measuring only 1.5mm x 1.5mm x 0.6mm :

Fig.3 : USP-8A01 Pin Configuration

It is possible to use a 1.0mm x 0.5mm x 0.5mm capacitor and a 1.0mm x 0.6mm x 0.5mm inductor.

Fig. 4 : XC2404 LNA Evaluation Board 20mm x 17.5mm