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, 50 V:
Output Power — 300 W
Gain — 14 dB (16 dB Typ)
Efficiency — 50%
• Low Thermal Resistance — 0.35°C/W
• Ruggedness Tested at Rated Output Power
• Nitride Passivated Die for Enhanced Reliability
D
Order this document
by MRF151G/D
300 W, 50 V, 175 MHz
N–CHANNEL
BROADBAND
RF POWER MOSFET
G
G
D
S
(FLANGE)
CASE 375–04, STYLE 2
MAXIMUM RATINGS
RatingSymbolValueUnit
Drain–Source VoltageV
Drain–Gate VoltageV
Gate–Source VoltageV
Drain Current — ContinuousI
Total Device Dissipation @ TC = 25°C
Derate above 25°C
Storage Temperature RangeT
Operating Junction TemperatureT
DSS
DGO
GS
D
P
D
stg
J
125Vdc
125Vdc
±40Vdc
40Adc
500
2.85
–65 to +150°C
200°C
THERMAL CHARACTERISTICS
CharacteristicSymbolMaxUnit
Thermal Resistance, Junction to CaseR
NOTE — CAUTION — MOS devices are susceptible to damage from electrostatic charge. Reasonable precautions in handling and
packaging MOS devices should be observed.
θJC
0.35°C/W
Watts
W/°C
REV 8
Motorola, Inc. 1997
MRF151GMOTOROLA RF DEVICE DATA
1
Page 2
ELECTRICAL CHARACTERISTICS (T
CharacteristicSymbolMinTypMaxUnit
= 25°C unless otherwise noted.)
C
OFF CHARACTERISTICS (Each Side)
Drain–Source Breakdown Voltage (VGS = 0, ID = 100 mA)V
Zero Gate Voltage Drain Current (VDS = 50 V, VGS = 0)I
Gate–Body Leakage Current (VGS = 20 V, VDS = 0)I
ON CHARACTERISTICS (Each Side)
Gate Threshold Voltage (VDS = 10 V, ID = 100 mA)V
Drain–Source On–Voltage (VGS = 10 V, ID = 10 A)V
Forward Transconductance (VDS = 10 V, ID = 5.0 A)g
DYNAMIC CHARACTERISTICS (Each Side)
Input Capacitance (VDS = 50 V, VGS = 0, f = 1.0 MHz)C
Output Capacitance (VDS = 50 V, VGS = 0, f = 1.0 MHz)C
Reverse Transfer Capacitance (VDS = 50 V, VGS = 0, f = 1.0 MHz)C
Unless Otherwise Noted, All Chip Capacitors are ATC Type 100 or
Equivalent.
Figure 1. 175 MHz Test Circuit
L2
C10C9
D.U.T.
T1 — 9:1 RF Transformer. Can be made of 15–18 Ohms
T1 — Semirigid Co–Ax, 62–90 Mils O.D.
T2 — 1:4 RF Transformer. Can be made of 16–18 Ohms
T2 — Semirigid Co–Ax, 70–90 Mils O.D.
Board Material — 0.062″ Fiberglass (G10),
1 oz. Copper Clad, 2 Sides, εr = 5.0
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 Figure 6 for construction details of T1 and T2.
T2
L1
C7C8
C11
C12
+
50 V
–
OUTPUT
MRF151G
2
MOTOROLA RF DEVICE DATA
Page 3
TYPICAL CHARACTERISTICS
1000
C
500
200
100
50
C, CAPACITANCE (pF)
20
0
0 1020304050
VDS, DRAIN–SOURCE VOLTAGE (VOL TS)
iss
C
oss
C
rss
Figure 2. Capacitance versus
Drain–Source Voltage*
*Data shown applies to each half of MRF151G.
1.04
1.03
1.02
1.01
1
0.99
0.98
0.97
0.96
0.95
0.94
0.93
0.92
, DRAIN-SOURCE VOLTAGE (NORMALIZED)
0.91
GS
0.9
V
–250255075100
TC, CASE TEMPERATURE (
250 mA
100 mA
°
C)
ID = 5 A
4 A
2 A
1 A
2000
VDS = 30 V
1000
, UNITY GAIN FREQUENCY (MHz)
T
f
0
048121620
26101418
I
, DRAIN CURRENT (AMPS)
D
15 V
Figure 3. Common Source Unity Gain Frequency
versus Drain Current*
100
TC = 25°C
10
, DRAIN CURRENT (AMPS)
D
I
1
220200
VDS, DRAIN–TO–SOURCE VOL TAGE (VOL TS)
Figure 4. Gate–Source V oltage versus
Case T emperature*
HIGH IMPEDANCE
WINDINGS
CENTER
CENTER
TAP
TAP
IMPEDANCE
Figure 6. RF Transformer
4:1
RATIO
Figure 5. DC Safe Operating Area
9:1
IMPEDANCE
RATIO
CONNECTIONS
TO LOW IMPEDANCE
WINDINGS
MRF151GMOTOROLA RF DEVICE DATA
3
Page 4
TYPICAL CHARACTERISTICS
350
f = 150 MHz
300
250
200
150
, OUTPUT POWER (WATTS)
100
out
P
50
0
0510
P
, INPUT POWER (WATTS)
in
VDD = 50 V
IDQ = 2 x 250 mA
175 MHz
200 MHz
30
25
20
15
, POWER GAIN (dB)
PS
G
10
5
VDD = 50 V
IDQ = 2 x 250 mA
P
= 150 W
out
251030100200
Figure 7. Output Power versus Input PowerFigure 8. Power Gain versus Frequency
f, FREQUENCY (MHz)
f = 175 MHz
150
125
INPUT, Z
in
150
125
f = 175 MHz
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.
Zo = 10
Ω
30
100
(GATE TO GATE)
100
30
Figure 9. Input and Output Impedance
MRF151G
4
MOTOROLA RF DEVICE DATA
Page 5
RF POWER MOSFET CONSIDERA TIONS
MOSFET CAPACITANCES
The physical structure of a MOSFET results in capacitors
between the terminals. The metal anode gate structure determines the capacitors from gate–to–drain (Cgd), and gate–
to–source (Cgs). The PN junction formed during the
fabrication of the RF MOSFET results in a junction capacitance from drain–to–source (Cds).
These capacitances are characterized as input (C
put (C
) and reverse transfer (C
oss
) capacitances on data
rss
iss
), out-
sheets. The relationships between the inter–terminal capacitances and those given on data sheets are shown below. The
C
can be specified in two ways:
iss
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.
DRAIN
C
ds
SOURCE
C
C
C
iss
oss
rss
= Cgd = C
= Cgd = C
= C
gd
gs
ds
GATE
C
gd
C
gs
LINEARITY AND GAIN CHARACTERISTICS
In addition to the typical IMD and power gain data presented, Figure 3 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 current 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 extent.
DRAIN CHARACTERISTICS
One figure of merit for a FET is its static resistance in the
full–on condition. This on–resistance, V
DS(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, V
has a positive temperature
DS(on)
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 gate–to–source threshold voltage,
V
GS(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 essentially capacitors. Circuits that leave the gate open–cir-
cuited 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 protection is required, an external zener diode is recommended.
Using a resistor to keep the gate–to–source 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 gate–drain capacitance. If the
gate–to–source 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 gate–threshold 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 applied. 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 MRF151G is an RF Power, MOS, N–channel enhancement mode field–effect 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 MRF151G is an enhancement mode FET and, therefore, 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 performance. The value of quiescent drain current (IDQ) is not critical for many applications. The MRF151G was characterized
at IDQ = 250 mA, each side, which is the suggested minimum
value of IDQ. For special applications such as linear amplification, IDQ may have to be selected to optimize the critical
parameters.
The gate is a dc open circuit and draws no current. Therefore, the gate bias circuit may be just a simple resistive divider network. Some applications may require a more elaborate
bias sytem.
GAIN CONTROL
Power output of the MRF151G 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.
Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty, representation or guarantee regarding
the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit,
and specifically disclaims any and all liability, including without limitation consequential or incidental damages. “T ypical” parameters can and do vary in different
applications. All operating parameters, including “T ypicals” must be validated for each customer application by customer’s technical experts. Motorola does
not convey any license under its patent rights nor the rights of others. Motorola products are not designed, intended, or authorized for use as components in
systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of
the Motorola product could create a situation where personal injury or death may occur. Should Buyer purchase or use Motorola products for any such
unintended or unauthorized application, Buyer shall indemnify and hold Motorola and its officers, employees, subsidiaries, affiliates, and distributors harmless
against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death
associated with such unintended or unauthorized use, even if such claim alleges that Motorola was negligent regarding the design or manufacture of the part.
Motorola and are registered trademarks of Motorola, Inc. Motorola, Inc. is an Equal Opportunity/Af firmative Action Employer.
How to reach us:
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MFAX: RMF AX0@email.sps.mot.com – T OUCHTONE (602) 244–6609HONG KONG: Motorola Semiconductors H.K. Ltd.; 8B Ta i Ping Industrial Park,
INTERNET: http://Design–NET.com51 Ting K ok Road, T ai Po, N.T., Hong Kong. 852–26629298
MRF151G6
◊
MOTOROLA RF DEVICE DATA
*MRF151G/D*
MRF151G/D
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