Highly efficient and matched low power linear RF (radio frequency) power amplifier

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Highly efficient and matched low power linear RF (radio frequency) power amplifier [Copy link]

Rapid Engineering Prototype (REP) #006 shows a custom solution for the MAX2269 linear power amplifier (PA) tuned for Japanese cellular CDMA applications. The PA is capable of providing 17% PAE at +16dBm output power in low-power mode. Please contact the factory for a detailed report of the application circuit and test data.

Rapid Engineering Models are actual circuits built and tested in our labs by Maxim applications engineers. They are the starting point for new RF engineering designs. They are not intended as evaluation test tools.

Objective: To develop and measure external switches to maximize the power added efficiency (PAE) of a PA (power amplifier) operating in the Japanese dual channel cellular band.

The PAE of the MAX2269 dual-channel power amplifier can be maximized by using an external (off-chip) high/low power amplifier switch. Since the separate external channel switches can be made using a semiconductor processing method based on the optimized characteristics of the switch, the main characteristics of the on-chip switch are slightly higher losses and slightly worse isolation (but the subsequent circuit cost is lower and smaller). Here, the chip is tuned for efficiency through the low-power path of the MAX2269 to obtain the longest battery life. This is because use in large urban areas will cause the average transmit power to be between -20dBm and -16dBm, and it is rarely necessary to use the high-power amplifier channel.

The MAX2269 linear RF power amplifier is designed for CDMA, PDC, and IS-136-based TDMA modulation formats in the Japanese cellular band. To achieve the best low-power PAE, the MAX2269 provides a dual-channel amplifier circuit with switching. Statistically, CDMA phones spend most of their time working in the low-power channel where PAE needs to be optimized (output is about +16dBm). By using an external FET switch or PIN diode, the MAX2269 provides the highest industry-leading PAE (typically 17%) in low-power mode.

Schematic of the MAX2269 Evaluation Kit (PDF, 47K)