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Maxim > Design Support > Technical Documents > Application Notes > Wireless and RF > APP 1005
Keywords: rf, rfic, pa, power amplifiers, transmitter, ism band, gsm, rf ics, integrated circuits
APPLICATION NOTE 1005
Ultra-Low Cost +30dBm PA for GSM and 900MHz-
ISM Applications
Sep 10, 2002
Abstract: This application note, based on the MAX2235 power amplifier (PA) shows the operation in
GSM and 900MHz ISM band applications. +30dBm of output power is achieved with 40 percent
efficiency. The device provides 24dB gain, and operates with a 2.7V to 5.5V power supply. A schematic,
the circuit board layout, and a bill of material are provided.
The MAX2235 is a low-cost, non-linear power amplifier, intended
for constant-envelope applications. Originally characterized for US
AMPS, this application note demonstrates the use of the device for
European GSM, 868MHz European-ISM and US 900MHz-ISM
band applications.
At 900MHz, the device delivers over +30dBm of output power at
40% efficiency, with 24dB of gain from a +5V supply. The device
can be operated from a single +2.7V to +5.5V voltage supply. A
gain-control pin allows the output power to be varied over a 35dB
range. A low-power shutdown mode reduces supply current
consumption to less than 1µA. A key feature of this PA is output power autoramping, which minimizes
transient noise and spectral splatter.
Figure 1 demonstrates the output power performance of the MAX2235 over the 880MHz to 915MHz
frequency band. Figures 2 through 4, demonstrate the output power, efficiency and supply current
performance of the MAX2235 versus input power and frequency. Figure 5 demonstrates the output
power of the MAX2235 versus gain control voltage.
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