MRF157_15 Datasheet, PDF (8/9 Pages) M/A-COM Technology Solutions, Inc. – Linear RF Power MOSFET

MRF157
Linear RF Power MOSFET
600W, to 80MHz
MOUNTING OF HIGH POWER RF
POWER TRANSISTORS
The package of this device is designed for conduction
cooling. It is extremely important to minimize the thermal
resistance between the device flange and the heat dissipa-
tor.
Since the device mounting flange is made of soft copper,
itmay be deformed during various stages of handling or
during transportation. It is recommended that the user
makes a final inspection on this before the device installa-
tion. ±0.0005, is considered sufficient for the flange bottom.
The same applies to the heat dissipator in the device
mounting area. If copper heat sink is not used, a copper
head spreader is strongly recommended between the de-
vice mounting surfaces and the main heat sink. It should be
at least 1/4, thick and extend at least one inch from the
flange edges. A thin layer of thermal compound in all inter-
faces is, of course, essential. The recommended torque on
the 4–40 mounting screws should be in the area of 4–5
lbs.–inch, and spring type lock washers along with flat
washers are recommended.
For die temperature calculations, the Δ temperature from a
corner mounting screw area to the bottom center of the
flange is approximately 5°C and 10°C under normal operat-
ing conditions (dissipation 150 W and 300 W respectively).
The main heat dissipater must be sufficiently large and
have low Rθ for moderate air velocity, unless liquid cooling
is employed.
M/A-COM Products
Released - Rev. 07.07
CIRCUIT CONSIDERATIONS
At high power levels (500 W and up), the circuit layout
becomes critical due to the low impedance levels and high
RF currents associated with the output matching. Some of
the components, such as capacitors and inductors must
also withstand these currents. The component losses are
directly proportional to the operating frequency. The manu-
facturers
specifications on capacitor ratings should be consulted on
these aspects prior to design.
Push–pull circuits are less critical in general, since the
ground referenced RF loops are practically eliminated, and
the impedance levels are higher for a given power output.
High power broadband transformers are also easier to de-
sign than comparable LC matching networks.
8
ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions • North America Tel: [phone] / Fax: [phone]
is considering for development. Performance is based on target specifications, simulated results,
and/or prototype measurements. Commitment to develop is not guaranteed.
PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology
Solutions has under development. Performance is based on engineering tests. Specifications are
• Europe Tel: [phone] / Fax: [phone]
• Asia/Pacific Tel: [phone] / Fax: [phone]
Visit www.macomtech.com for additional data sheets and product information.
typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. _{M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make}
Commitment to produce in volume is not guaranteed.
changes to the product(s) or information contained herein without notice.