MRF1517NT1
13
RF Device Data
Freescale Semiconductor
MOUNTING
The specified maximum thermal resistance of 2°C/W as-
sumes a majority of the 0.065″ x 0.180″ 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 Freescale 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 Freescale 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 Free-
scale Application Note AN215A, “RF Small -Signal Design
Using Two-Port Parameters” for a discussion of two port
network theory and stability.
