MRF157 - M/A-COM Technology Solutions

Linear RF Power MOSFET

600W, to 80MHz

Rev. V1

MRF157

M/A-COM Technology Solutions Inc. (MACOM) and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice.

Visit www.macom.com for additional data sheets and product information.

For further information and support please visit:

https://www.macom.com/support

Product Image

Designed primarily for linear large signal output stages

to 80 MHz.

 Specified 50 volts, 30 MHz characteristics

Output power = 600 watts

Power gain = 21 dB (typ.)

Efficiency = 45% (typ.)

Linear RF Power MOSFET

600W, to 80MHz

Rev. V1

MRF157

M/A-COM Technology Solutions Inc. (MACOM) and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice.

Visit www.macom.com for additional data sheets and product information.

For further information and support please visit:

https://www.macom.com/support

Linear RF Power MOSFET

600W, to 80MHz

Rev. V1

MRF157

M/A-COM Technology Solutions Inc. (MACOM) and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice.

Visit www.macom.com for additional data sheets and product information.

For further information and support please visit:

https://www.macom.com/support

Linear RF Power MOSFET

600W, to 80MHz

Rev. V1

MRF157

M/A-COM Technology Solutions Inc. (MACOM) and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice.

Visit www.macom.com for additional data sheets and product information.

For further information and support please visit:

https://www.macom.com/support

Linear RF Power MOSFET

600W, to 80MHz

Rev. V1

MRF157

M/A-COM Technology Solutions Inc. (MACOM) and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice.

Visit www.macom.com for additional data sheets and product information.

For further information and support please visit:

https://www.macom.com/support

Linear RF Power MOSFET

600W, to 80MHz

Rev. V1

MRF157

M/A-COM Technology Solutions Inc. (MACOM) and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice.

Visit www.macom.com for additional data sheets and product information.

For further information and support please visit:

https://www.macom.com/support

Linear RF Power MOSFET

600W, to 80MHz

Rev. V1

MRF157

M/A-COM Technology Solutions Inc. (MACOM) and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice.

Visit www.macom.com for additional data sheets and product information.

For further information and support please visit:

https://www.macom.com/support

RF POWER MOSFET CONSIDERATIONS

MOSFET CAPACITANCES

The physical structure of a MOSFET results in capacitors

between the terminals. The metal oxide gate structure de-

termines the capacitors from gate–to–drain (Cgd), and gate

–to–source (Cgs). The PN junction formed during the fabri-

cation of the RF MOSFET results in a junction capacitance

from drain–to–source (Cds).

These capacitances are characterized as input (Ciss),

output (Coss) and reverse transfer (Crss) capacitances on

data sheets. The relationships between the inter–terminal

capacitances and those given on data sheets are shown

below. The

Ciss can be specified in two ways:

1. Drain shorted to source and positive voltage at the

gate.

2. Positive voltage of the drain in respect to source and

zero volts at the gate. In the latter case the numbers

are lower. However, neither method represents the

actual operating conditions in RF applications.

LINEARITY AND GAIN CHARACTERISTICS

In addition to the typical IMD and power gain data pre-

sented, Figure 5 may give the designer additional informa-

tion on the capabilities of this device. The graph represents

the small signal unity current gain frequency at a given

drain current level. This is equivalent to fT for bipolar tran-

sistors. Since this test is performed at a fast sweep speed,

heating of the device does not occur. Thus, in normal use,

the higher temperatures may degrade these characteristics

to some extent.

DRAIN CHARACTERISTICS

One figure of merit for a FET is its static resistance in the

full–on condition. This on–resistance, VDS(on), occurs in

the linear region of the output characteristic and is specified

under specific test conditions for gate–source voltage and

drain current. For MOSFETs, VDS(on) has a positive tem-

perature coefficient and constitutes an important design

consideration at high temperatures, because it contributes

to the power dissipation within the device.

GATE CHARACTERISTICS

The gate of the RF MOSFET is a polysilicon material, and

is electrically isolated from the source by a layer of oxide.

The input resistance is very high — on the order of 109

ohms

— resulting in a leakage current of a few nanoamperes.

Gate control is achieved by applying a positive voltage

slightly in excess of the gate–to–source threshold voltage,

VGS(th).

Gate Voltage Rating — Never exceed the gate voltage

rating. Exceeding the rated VGS can result in permanent

damage to the oxide layer in the gate region.

Gate Termination — The gates of these devices are es-

sentially capacitors. Circuits that leave the gate open–

circuited or floating should be avoided. These conditions

can result in turn–on of the devices due to voltage build–up

on the input capacitor due to leakage currents or pickup.

Gate Protection — These devices do not have an internal

monolithic zener diode from gate–to–source. If gate protec-

tion is required, an external zener diode is recommended.

IMPEDANCE CHARACTERISTICS

Device input and output impedances are normally ob-

tained by measuring their conjugates in an optimized nar-

row band test circuit. These test circuits are designed and

constructed for a number of frequency points depending on

the frequency coverage of characterization. For low fre-

quencies the circuits consist of standard LC matching net-

works including variable capacitors for peak tuning. At in-

creasing power levels the output impedance decreases,

resulting in higher RF currents in the matching network.

This makes the practicality of output impedance measure-

ments in the manner described questionable at power lev-

els higher than 200–300 W for devices operated at 50 V

and 150–200 W for devices operated at 28 V. The physical

sizes and values required for the components to withstand

the RF currents increase to a point where physical con-

struction of the output matching network gets difficult if not

impossible. For this reason the output impedances are not

given for high power devices such as the MRF154 and

MRF157.

However, formulas like for a single ended

d e s i g n or for a push–pull design can be

used to obtain reasonably close approximations to actual

values.

Linear RF Power MOSFET

600W, to 80MHz

Rev. V1

MRF157

M/A-COM Technology Solutions Inc. (MACOM) and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice.

Visit www.macom.com for additional data sheets and product information.

For further information and support please visit:

https://www.macom.com/support

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  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 R for moderate air velocity, unless liquid cooling

is employed.

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.

Linear RF Power MOSFET

600W, to 80MHz

Rev. V1

MRF157

M/A-COM Technology Solutions Inc. (MACOM) and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice.

Visit www.macom.com for additional data sheets and product information.

For further information and support please visit:

https://www.macom.com/support

Linear RF Power MOSFET

600W, to 80MHz

Rev. V1

MRF157

M/A-COM Technology Solutions Inc. (MACOM) and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice.

Visit www.macom.com for additional data sheets and product information.

For further information and support please visit:

https://www.macom.com/support

Information in this document is provided in connection with M/A-COM Technology Solutions Inc ("MACOM")

products. These materials are provided by MACOM as a service to its customers and may be used for

informational purposes only. Except as provided in MACOM's Terms and Conditions of Sale for such products or

in any separate agreement related to this document, MACOM assumes no liability whatsoever. MACOM

assumes no responsibility for errors or omissions in these materials. MACOM may make changes to

specifications and product descriptions at any time, without notice. MACOM makes no commitment to update

the information and shall have no responsibility whatsoever for conflicts or incompatibilities arising from future

changes to its specifications and product descriptions. No license, express or implied, by estoppels or otherwise,

to any intellectual property rights is granted by this document.

THESE MATERIALS ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR

IMPLIED, RELATING TO SALE AND/OR USE OF MACOM PRODUCTS INCLUDING LIABILITY OR

WARRANTIES RELATING TO FITNESS FOR A PARTICULAR PURPOSE, CONSEQUENTIAL OR

INCIDENTAL DAMAGES, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR

OTHER INTELLECTUAL PROPERTY RIGHT. MACOM FURTHER DOES NOT WARRANT THE ACCURACY

OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN

THESE MATERIALS. MACOM SHALL NOT BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL, OR

CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS,

WHICH MAY RESULT FROM THE USE OF THESE MATERIALS.

MACOM products are not intended for use in medical, lifesaving or life sustaining applications. MACOM

customers using or selling MACOM products for use in such applications do so at their own risk and agree to

fully indemnify MACOM for any damages resulting from such improper use or sale.