RFHA3944 Datasheet, PDF (11/11 Pages) RF Micro Devices – 65W GaN Wide-Band Power Amplifier

RFHA3944
Device Handling/Environmental Conditions
RFMD does not recommend operating this device with typical drain voltage applied and the gate pinched off in a high
humidity, high temperature environment.
GaN HEMT devices are ESD sensitive materials. Please use proper ESD precautions when handling devices or evaluation
boards.
GaN HEMT Capacitances
The physical structure of the GaN HEMT results in three terminal capacitors similar to other FET technologies. These
capacitances exist across all three terminals of the device. The physical manufactured characteristics of the device determine the
value of the C_DS (drain to source), C_GS (gate to source) and C_GD (gate to drain). These capacitances change value as the terminal
voltages are varied. RFMD presents the three terminal capacitances measured with the gate pinched off (V_GS = -8V) and zero volts
applied to the drain. During the measurement process, the parasitic capacitances of the package that holds the amplifier is
removed through a calibration step. Any internal matching is included in the terminal capacitance measurements. The capacitance
values presented in the typical characteristics table of the device represent the measured input (C_ISS), output (C_OSS), and reverse
(C_RSS) capacitance at the stated bias voltages. The relationship to three terminal capacitances is as follows:
C_ISS = C_GD + C_GS
C_OSS = C_GD + C_DS
C_RSS = C_GD
DC Bias
The GaN HEMT device is a depletion mode high electron mobility transistor (HEMT). At zero volts V_GS the drain of the device is
saturated and uncontrolled drain current will destroy the transistor. The gate voltage must be taken to a potential lower than the
source voltage to pinch off the device prior to applying the drain voltage, taking care not to exceed the gate voltage maximum
limits. RFMD recommends applying V_GS = -5V before applying any V_DS.
RF Power transistor performance capabilities are determined by the applied quiescent drain current. This drain current can be
adjusted to trade off power, linearity, and efficiency characteristics of the device. The recommended quiescent drain current (I_DQ)
shown in the RF typical performance table is chosen to best represent the operational characteristics for this device, considering
manufacturing variations and expected performance. The user may choose alternate conditions for biasing this device based on
performance tradeoffs.
Mounting and Thermal Considerations
The thermal resistance provided as R_TH (junction to case) represents only the packaged device thermal characteristics. This is
measured using IR microscopy capturing the device under test temperature at the hottest spot of the die. At the same time, the
package temperature is measured using a thermocouple touching the backside of the die embedded in the device heatsink but
sized to prevent the measurement system from impacting the results. Knowing the dissipated power at the time of the
measurement, the thermal resistance is calculated.
In order to achieve the advertised MTTF, proper heat removal must be considered to maintain the junction at or below the
maximum of 200°C. Proper thermal design includes consideration of ambient temperature and the thermal resistance from
ambient to the back of the package including heatsinking systems and air flow mechanisms. Incorporating the dissipated DC
power, it is possible to calculate the junction temperature of the device.
RF Micro Devices Inc. 7628 Thorndike Road, Greensboro, NC 27409-9421
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For sales or technical support, contact RFMD at +1.336.678.5570 or [e-mail].
The information in this publication is believed to be accurate. However, no responsibility is assumed by RF Micro Devices, Inc. ("RFMD") for its use, nor for any infringement of patents or other rights of
third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent rights of RFMD. RFMD reserves the right to change component circuitry, recommended
application circuitry and specifications at any time without prior notice.
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