MRF1550T1 Datasheet, PDF (9/12 Pages) Motorola, Inc – RF POWER FIELD EFFECT TRANSISTORS

Freescale Semiconductor, Inc.
MOUNTING
The specified maximum thermal resistance of 0.75°C/W
assumes a majority of the 0.170″ x 0.608″ source contact on
the back side of the package is in good contact with an ap-
propriate heat sink. As with all RF power devices, the goal of
the thermal design should be to minimize the temperature at
the back side of the package. Refer to Motorola Application
Note AN4005/D, “Thermal Management and Mounting Meth-
od for the PLD–1.5 RF Power Surface Mount Package,” and
Engineering Bulletin EB209/D, “Mounting Method for RF
Power Leadless Surface Mount Transistor” for additional in-
formation.
AMPLIFIER DESIGN
Impedance matching networks similar to those used with
bipolar transistors are suitable for this device. For examples
see Motorola Application Note AN721, “Impedance Matching
Networks Applied to RF Power Transistors.” Large–signal
impedances are provided, and will yield a good first pass
approximation.
Since RF power MOSFETs are triode devices, they are not
unilateral. This coupled with the very high gain of this device
yields a device capable of self oscillation. Stability may be
achieved by techniques such as drain loading, input shunt
resistive loading, or output to input feedback. The RF test fix-
ture implements a parallel resistor and capacitor in series
with the gate, and has a load line selected for a higher effi-
ciency, lower gain, and more stable operating region.
Two–port stability analysis with this device’s
S–parameters provides a useful tool for selection of loading
or feedback circuitry to assure stable operation. See
Motorola Application Note AN215A, “RF Small–Signal
Design Using Two–Port Parameters” for a discussion of two
port network theory and stability.
MOTOROLA RF DEVICE DATA
For More Information On This Product,
Go to: www.freescale.com
MRF1550T1 MRF1550FT1
9