RF2138
Typical Test Setup
Power Supply
V- S- S+ V+
2
RF Generator
Spectrum
Analyzer
3dB
10dB/5W
Buffer
x1 OpAmp
Puls
Generator
A buffer amplifier is recommended because the current into
the Vapc changes with voltage. As an alternative, the
voltage may be monitored with an oscilloscope.
Notes about testing the RF2138
The test setup shown above includes two attenuators. The 3dB pad at the input is to minimize the effects that the
switching of the input impedance of the PA has on the signal generator. When Vapc is switched quickly, the resulting
input impedance change can cause the signal generator to vary its output signal, either in output level or in frequency.
Instead of an attenuator an isolator may also be used. The attenuator at the output is to prevent damage to the spec-
trum analyzer, and should be able to handle the power.
It is important not to exceed the rated supply current and output power. When testing the device at higher than nominal
supply voltage, the VAPC should be adjusted to avoid the output power exceeding +36dBm. During load-pull testing at
the output it is important to monitor the forward power through a directional coupler. The forward power should not
exceed +36dBm, and VAPC needs to be adjusted accordingly. This simulates the behavior for the power control loop in
this respect. To avoid damage, it is recommended to set the power supply to limiting the current during the burst, not to
exceed the maximum current rating.
Rev A9 011031
2-127
RFMD [ RF MICRO DEVICES ]
