Reference Circuit 1088

REP014: CDMA PA provides -45dBc ACPR at +28.5dBm



Rapid Engineering Prototypes are real circuits that Maxim application engineers have built and measured in our labs. They can provide a starting point for new RF designs. They are not available as evaluation kits.


Objective: For this low-cost CDMA cellular PA, to develop an application circuit that offers good linearity with good power-added efficiency (PAE).

The project requirement was to tune the MAX2265 RF power amplifier in a cellular-band CDMA handset to meet 28.5dBm power output with -45dBc ACPR1 and 34% PAE. The EV board was used initially for the tuning and the tests.

The MAX2265 linear RF power amplifier is designed for U.S. cellular-band IS-95-based CDMA, PDC, and IS-136-based TDMAmodulation formats. To improve its PAE, the MAX2265 offers a continuous-bias-current throttle-back arrangement. In this way, the amplifier linearity (that is, the adjacent-channel power ratio, or ACPR) is held relatively constant, whereas both the output power and the current drain are reduced. Thus, the desired linearity can be maintained, while improving low-output PAE, over a continuously variable output control range.

Schematic of the MAX2265 evaluation lit (PDF, 39kB)
Performance results of the MAX2265
Bill of materials, part 1
Bill of materials, part 2

 


 
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MAX2265
2.7V, Single-Supply, Cellular-Band Linear Power Amplifiers

  • Low Average CDMA Current Consumption in Typical Urban Scenario
  • 0.5µA Shutdown Mode Eliminates External Supply Switch
  • ±0.8dB Gain Variation Over Temperature