TA0012 Просмотр технического описания (PDF) - RF Micro Devices
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TA0012 Datasheet PDF : 4 Pages
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TA0012
• To utilize a GaAs MESFET power amplifier, the sys-
tem designer must insert a switch into the bias sup-
ply line to the part for shutdown. The gate cannot be
used to switch the MESFET on and off due to the
high gate-source capacitance. On-board charge
pumps must consume milliamps of current during
power-down. This supply-side switch must be capa-
ble of supporting very high currents, and tends to be
very ex-pensive as a result. A MOSFET switch will
cost on the order of $0.50 to $0.75, which is a sub-
stantial portion of the overall power amplifier cost.
The loss through the switch also reduces the volt-
age available on the drain of the MESFET PA, thus
requiring more current to achieve the same output
power.
• Gain Control. Using the same pin as is used for
power down, the gain is controlled over 60dB with a
1V to 4V control range. A typical power control
characteristic is shown in Figure 1.
• High Reliability. At RF Micro Devices, we have
logged over 1.5 million device hours under RF
stress accelerated lifetest since 1993. Junction tem-
peratures of 250°C are used to accelerate the test.
In addition, TRW has been running accelerated DC
lifetest, which correlate with RF stress results. The
reliability is much improved over the initial HBT
technologies available 8-10 years ago. Today, over
40 million hours MTBF at 125°C junction tempera-
tures is achieved.
13
Figure 1. Output power vs. Vpc from 0 to 4V. Note that the power control range is >60dB with
the maximum output power at 36.3dBm.
The RF2123 is one of a family of power amplifiers from
RF Micro Devices based upon HBT technology for both
linear and constant-envelope applications. This tech-
nology, provided by TRW, is a proven technology origi-
nally developed for military and space applications.
Based upon a Gallium Arsenide/Aluminum Gallium
Arsenide (GaAs/AlGaAs) heterostructure, the power
and efficiency performance is the highest of any com-
mercially available integrated solution. Being a bipolar
structure, the part can operate from a single positive
voltage supply without adding components – extremely
important in a battery operated system such as a cellu-
lar phone.
The critical geometries in an HBT transistor are vertical
structures, not lateral. The emitter, base, and collector
are stacked vertically by semiconductor layer growth,
using MBE (Molecular Beam Epitaxy). This is a very
accurate and repeatable growth process. Since each
layer is placed over the entire wafer at once, no photo-
13-64
Copyright 1997-2000 RF Micro Devices, Inc.
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