MRF141G

MOTOROLA RF DEVICE DATA

The RF MOSFET Line

RF Power Field-Effect Transistor

NChannel EnhancementMode MOSFET

Designed for broadband commercial and military applications at frequencies

to 175 MHz. The high power, high gain and broadband performance of this
device makes possible solid state transmitters for FM broadcast or TV channel
frequency bands.

Guaranteed Performance at 175 MHz, 28 V:

Output Power -- 300 W
Gain -- 12 dB (14 dB Typ)
Efficiency -- 50%

Low Thermal Resistance -- 0.35

C/W

Ruggedness Tested at Rated Output Power

Nitride Passivated Die for Enhanced Reliability

MAXIMUM RATINGS

Rating

Symbol

Value

Unit

DrainSource Voltage

VDSS

Vdc

DrainGate Voltage

VDGO

Vdc

GateSource Voltage

VGS

Vdc

Drain Current -- Continuous

Adc

Total Device Dissipation @ TC = 25

Derate above 25

500

2.85

Watts

Storage Temperature Range

Tstg

65 to +150

Operating Junction Temperature

200

THERMAL CHARACTERISTICS

Characteristic

Symbol

Max

Unit

Thermal Resistance, Junction to Case

0.35

C/W

NOTE -- CAUTION -- MOS devices are susceptible to damage from electrostatic charge. Reasonable precautions in handling and
packaging MOS devices should be observed.

Order this document

by MRF141G/D

MOTOROLA

SEMICONDUCTOR TECHNICAL DATA

MRF141G

300 W, 28 V, 175 MHz

NCHANNEL

BROADBAND

RF POWER MOSFET

CASE 37504, STYLE 2

Motorola, Inc. 1997

(FLANGE)

REV 2

MRF141G
2

MOTOROLA RF DEVICE DATA

ELECTRICAL CHARACTERISTICS

(TC = 25

C unless otherwise noted)

Characteristic

Symbol

Min

Typ

Max

Unit

OFF CHARACTERISTICS (1)

DrainSource Breakdown Voltage

(VGS = 0, ID = 100 mA)

V(BR)DSS

Vdc

Zero Gate Voltage Drain Current

(VDS = 28 V, VGS = 0)

IDSS

5.0

mAdc

GateBody Leakage Current

(VGS = 20 V, VDS = 0)

IGSS

1.0

Adc

ON CHARACTERISTICS (1)

Gate Threshold Voltage

(VDS = 10 V, ID = 100 mA)

VGS(th)

1.0

3.0

5.0

Vdc

DrainSource OnVoltage

(VGS = 10 V, ID = 10 A)

VDS(on)

0.1

0.9

1.5

Vdc

Forward Transconductance

(VDS = 10 V, ID = 5.0 A)

gfs

5.0

7.0

mhos

DYNAMIC CHARACTERISTICS (1)

Input Capacitance

(VDS = 28 V, VGS = 0, f = 1.0 MHz)

Ciss

350

Output Capacitance

(VDS = 28 V, VGS = 0, f = 1.0 MHz)

Coss

420

Reverse Transfer Capacitance

(VDS = 28 V, VGS = 0, f = 1.0 MHz)

Crss

FUNCTIONAL TESTS (2)

Common Source Amplifier Power Gain

(VDD = 28 V, Pout = 300 W, IDQ = 500 mA, f = 175 MHz)

Gps

Drain Efficiency

(VDD = 28 V, Pout = 300 W, f = 175 MHz, ID (Max) = 21.4 A)

Load Mismatch

(VDD = 28 V, Pout = 300 W, IDQ = 500 mA, f = 175 MHz,
VSWR 5:1 at all Phase Angles)

No Degradation in Output Power

NOTES:

1. Each side measured separately.
2. Measured in pushpull configuration.

MRF141G

MOTOROLA RF DEVICE DATA

Figure 1. 175 MHz Test Circuit

C1 -- Arco 402, 1.5 20 pF
C2 -- Arco 406, 15 115 pF
C3, C4, C8, C9, C10 -- 1000 pF Chip
C5, C11 -- 0.1

F Chip

C6 -- 330 pF Chip
C7 -- 200 pF and 180 pF Chips in Parallel
C12 -- 0.47

F Ceramic Chip, Kemet 1215 or Equivalent

C13 -- Arco 403, 3.0 35 pF
L1 -- 10 Turns AWG #16 Enameled Wire,

L1 --

Close Wound, 1/4

I.D.

L2 -- Ferrite Beads of Suitable Material for

L2 --

1.5 2.0

H Total Inductance

R1 -- 100 Ohms, 1/2 W
R2 -- 1.0 kOhm, 1/2 W

Unless Otherwise Noted, All Chip Capacitors are ATC Type 100 or Equivalent.

T1 -- 9:1 RF Transformer. Can be made of 15 18 Ohms

T1 --

Semirigid CoAx, 62 90 Mils O.D.

T2 -- 1:9 RF Transformer. Can be made of 15 18 Ohms

T2 --

Semirigid CoAx, 70 90 Mils O.D.

Board Material -- 0.062

Fiberglass (G10),

1 oz. Copper Clad, 2 Sides,

r = 5

NOTE: For stability, the input transformer T1 must be loaded

NOTE:

with ferrite toroids or beads to increase the common

NOTE:

mode inductance. For operation below 100 MHz. The

NOTE:

same is required for the output transformer.

See pictures for construction details.

Figure 2. DC Safe Operating Area

Figure 3. GateSource Voltage versus

Case Temperature

TYPICAL CHARACTERISTICS

BIAS 0 6 V

INPUT

C10

C11

C12

28 V

OUTPUT

C13

100

VDS, DRAINTOSOURCE VOLTAGE (VOLTS)

I D

, DRAIN CURRENT

(AMPS)

TC = 25

, GA

TE-SOURCE

VOL

T
AGE

(NORMALIZED)

1.04

TC, CASE TEMPERATURE (

1.03
1.02
1.01

0.99
0.98
0.97
0.96
0.95
0.94
0.93
0.92
0.91

0.9

100

ID = 5 A

4 A

2 A

1 A

0.5 A

0.25 A

DUT

HIGH

IMPEDANCE

WINDINGS

CENTER

TAP

4:1

IMPEDANCE

RATIO

9:1

IMPEDANCE

RATIO

CONNECTIONS

TO LOW

IMPEDANCE

WINDINGS

CENTER

TAP

MRF141G
4

MOTOROLA RF DEVICE DATA

Figure 4. Common Source Unity Gain Frequency

versus Drain Current

Figure 5. Capacitance versus

DrainSource Voltage

Figure 6. Power Gain versus Frequency

TYPICAL CHARACTERISTICS

Figure 7. Output Power versus Supply Voltage

2000

ID, DRAIN CURRENT (AMPS)

1000

2000

200

VDS, DRAINTOSOURCE VOLTAGE (VOLTS)

VDS = 20 V

10 V

NOTE: Data shown applies to each half of MRF141G.

,
UNITY

GAIN FREQUENCY

(MHz)

C, CAP

ACIT

ANCE

(pF)

NOTE: Data shown applies to each half of MRF141G.

Coss

Ciss

Crss

, POWER GAIN (dB)

f, FREQUENCY (MHz)

100

200

VDD = 28 V

IDQ = 2 x 250 mA

Pout = 300 W

400

SUPPLY VOLTAGE (VOLTS)

, OUTPUT

POWER

TTS)

out

350

300

250

200

150

100

Figure 8. Input and Output Impedances

f = 175 MHz

IDQ = 250 mA x 2

Pin = 30 W

20 W

10 W

Zo = 10

f = 175 MHz

INPUT, Zin

(GATE TO GATE)

100

150

125

f = 175 MHz

150

125

100

OUTPUT, ZOL*

(DRAIN TO DRAIN)

ZOL* = Conjugate of the optimum load impedance

ZOL* =

into which the device output operates at a

ZOL* =

given output power, voltage and frequency.

MRF141G

MOTOROLA RF DEVICE DATA

RF POWER MOSFET CONSIDERATIONS

MOSFET CAPACITANCES

The physical structure of a MOSFET results in capacitors

between the terminals. The metal anode gate structure de-
termines the capacitors from gatetodrain (Cgd), and gate
tosource (Cgs). The PN junction formed during the
fabrication of the MOSFET results in a junction capacitance
from draintosource (Cds).

These capacitances are characterized as input (Ciss), out-

put (Coss) and reverse transfer (Crss) capacitances on data
sheets. The relationships between the interterminal capaci-
tances 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 operat-
ing conditions in RF applications.

Cgd

GATE

SOURCE

Cgs

DRAIN

Cds

Ciss = Cgd = Cgs

Coss = Cgd = Cds

Crss = Cgd

LINEARITY AND GAIN CHARACTERISTICS

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

ented, Figure 4 may give the designer additional information
on the capabilities of this device. The graph represents the
small signal unity current gain frequency at a given drain cur-
rent level. This is equivalent to fT for bipolar transistors.
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 ex-
tent.

DRAIN CHARACTERISTICS

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

fullon condition. This onresistance, VDS(on), occurs in the
linear region of the output characteristic and is specified un-
der specific test conditions for gatesource voltage and drain
current. For MOSFETs, VDS(on) has a positive temperature
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 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 gatetosource 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 gate of this device is essentially

capacitor. Circuits that leave the gate opencircuited or float-

ing should be avoided. These conditions can result in turn
on of the device due to voltage buildup on the input
capacitor due to leakage currents or pickup.

Gate Protection -- This device does not have an internal

monolithic zener diode from gatetosource. If gate protec-
tion is required, an external zener diode is recommended.

Using a resistor to keep the gatetosource impedance

low also helps damp transients and serves another important
function. Voltage transients on the drain can be coupled to
the gate through the parasitic gatedrain capacitance. If the
gatetosource impedance and the rate of voltage change
on the drain are both high, then the signal coupled to the gate
may be large enough to exceed the gatethreshold voltage
and turn the device on.

HANDLING CONSIDERATIONS

When shipping, the devices should be transported only in

antistatic bags or conductive foam. Upon removal from the
packaging, careful handling procedures should be adhered
to. Those handling the devices should wear grounding straps
and devices not in the antistatic packaging should be kept in
metal tote bins. MOSFETs should be handled by the case
and not by the leads, and when testing the device, all leads
should make good electrical contact before voltage is ap-
plied. As a final note, when placing the FET into the system it
is designed for, soldering should be done with a grounded
iron.

DESIGN CONSIDERATIONS

The MRF141G is an RF Power, MOS, Nchannel en-

hancement mode fieldeffect transistor (FET) designed for
HF and VHF power amplifier applications.

Motorola Application Note AN211A, FETs in Theory and

Practice, is suggested reading for those not familiar with the
construction and characteristics of FETs.

The major advantages of RF power MOSFETs include

high gain, low noise, simple bias systems, relative immunity
from thermal runaway, and the ability to withstand severely
mismatched loads without suffering damage. Power output
can be varied over a wide range with a low power dc control
signal.

DC BIAS

The MRF141G is an enhancement mode FET and, there-

fore, does not conduct when drain voltage is applied. Drain
current flows when a positive voltage is applied to the gate.
RF power FETs require forward bias for optimum perfor-
mance. The value of quiescent drain current (IDQ) is not criti-
cal for many applications. The MRF141G was characterized
at IDQ = 250 mA, each side, which is the suggested minimum
value of IDQ. For special applications such as linear amplifi-
cation, IDQ may have to be selected to optimize the critical
parameters.

The gate is a dc open circuit and draws no current. There-

fore, the gate bias circuit may be just a simple resistive divid-
er network. Some applications may require a more elaborate
bias sytem.

GAIN CONTROL

Power output of the MRF141G may be controlled from its

rated value down to zero (negative gain) by varying the dc
gate voltage. This feature facilitates the design of manual
gain control, AGC/ALC and modulation systems.

Part Number MRF141G