5.2–51
MRF1511T1MOTOROLA WIRELESS
RF PRODUCT DEVICE DATA
The RF MOSFET Line
N–Channel Enhancement–Mode Lateral MOSFET
The MRF1511T1 is designed for broadband commercial and industrial
applications at frequencies to 175 MHz. The high gain and broadband
performance of this device makes it ideal for large–signal, common source
amplifier applications in 7.5 volt portable FM equipment.
•Specified Performance @ 175 MHz, 7.5 Volts
Output Power — 8 Watts
Power Gain — 11.5 dB
Efficiency — 55%
•Capable of Handling 20:1 VSWR, @ 9.5 Vdc,
175 MHz, 2 dB Overdrive
•Excellent Thermal Stability
•Characterized with Series Equivalent Large–Signal
Impedance Parameters
•Broadband UHF/VHF Demonstration Amplifier Information
Available Upon Request
•RF Power Plastic Surface Mount Package
•Available in Tape and Reel.
T1 Suffix = 1,000 Units per 12 mm, 7 Inch Reel.
MAXIMUM RATINGS
Rating Symbol Value Unit
Drain–Source Voltage VDSS 40 Vdc
Gate–Source Voltage VGS ±20 Vdc
Drain Current — Continuous ID4 Adc
Total Device Dissipation @ TC = 25°C (1)
Derate above 25°CPD62.5
0.5 Watts
W/°C
Storage Temperature Range Tstg –65 to +150 °C
Operating Junction Temperature TJ150 °C
THERMAL CHARACTERISTICS
Characteristic Symbol Max Unit
Thermal Resistance, Junction to Case RθJC 2°C/W
(1) Calculated based on the formula PD = TJ–TC
RθJC
NOTE – CAUTION – MOS devices are susceptible to damage from electrostatic charge. Reasonable precautions in handling and
packaging MOS devices should be observed.
SEMICONDUCTOR TECHNICAL DATA
175 MHz, 8 W, 7.5 V
LATERAL N–CHANNEL
BROADBAND
RF POWER MOSFET
CASE 466–02, STYLE 1
(PLD–1.5)
PLASTIC
REV 1
MRF1511T1
5.2–52 MOTOROLA WIRELESS
RF PRODUCT DEVICE DATA
ELECTRICAL CHARACTERISTICS (TC = 25°C unless otherwise noted)
Characteristic Symbol Min Typ Max Unit
OFF CHARACTERISTICS
Zero Gate Voltage Drain Current
(VDS = 35 Vdc, VGS = 0) IDSS — — 1 µAdc
Gate–Source Leakage Current
(VGS = 10 Vdc, VDS = 0) IGSS — — 1 µAdc
ON CHARACTERISTICS
Gate Threshold Voltage
(VDS = 7.5 Vdc, ID = 170 µA) VGS(th) 1.0 1.6 2.1 Vdc
Drain–Source On–Voltage
(VGS = 10 Vdc, ID = 1 Adc) VDS(on) — 0.4 — Vdc
DYNAMIC CHARACTERISTICS
Input Capacitance
(VDS = 7.5 Vdc, VGS = 0, f = 1 MHz) Ciss — 100 — pF
Output Capacitance
(VDS = 7.5 Vdc, VGS = 0, f = 1 MHz) Coss — 53 — pF
Reverse Transfer Capacitance
(VDS = 7.5 Vdc, VGS = 0, f = 1 MHz) Crss — 8 — pF
FUNCTIONAL TESTS (In Motorola Test Fixture)
Common–Source Amplifier Power Gain
(VDD = 7.5 Vdc, Pout = 8 Watts, IDQ = 150 mA, f = 175 MHz) Gps 10 11.5 — dB
Drain Efficiency
(VDD = 7.5 Vdc, Pout = 8 Watts, IDQ = 150 mA, f = 175 MHz) η50 55 — %
5.2–53
MRF1511T1MOTOROLA WIRELESS
RF PRODUCT DEVICE DATA
Figure 1. 135 – 175 MHz Broadband Test Circuit
B1, B2 Short Ferrite Bead, Fair Rite Products
(2743021446)
C1, C5, C18 120 pF, 100 mil Chip Capacitor
C2, C10, C12 0 to 20 pF, Trimmer Capacitor
C3 33 pF, 100 mil Chip Capacitor
C4 68 pF, 100 mil Chip Capacitor
C6, C15 10 µF, 50 V Electrolytic Capacitor
C7, C16 1,200 pF, 100 mil Chip Capacitor
C8, C17 0.1 µF, 100 mil Chip Capacitor
C9 150 pF, 100 mil Chip Capacitor
C11 43 pF, 100 mil Chip Capacitor
C13 24 pF, 100 mil Chip Capacitor
C14 300 pF, 100 mil Chip Capacitor
L1, L3 12.5 nH, A04T, Coilcraft
L2 26 nH, 4 Turn, Coilcraft
L4 55.5 nH, 5 Turn, Coilcraft
N1, N2 Type N Flange Mount
R1 15 Ω, 0805 Chip Resistor
R2 1.0 kΩ, 1/8 W Resistor
R3 1.0 kΩ, 0805 Chip Resistor
R4 33 kΩ, 1/8 W Resistor
Z1 0.200″ x 0.080″ Microstrip
Z2 0.755″ x 0.080″ Microstrip
Z3 0.300″ x 0.080″ Microstrip
Z4 0.065″ x 0.080″ Microstrip
Z5, Z6 0.260″ x 0.223″ Microstrip
Z7 0.095″ x 0.080″ Microstrip
Z8 0.418″ x 0.080″ Microstrip
Z9 1.057″ x 0.080″ Microstrip
Z10 0.120″ x 0.080″ Microstrip
Board Glass Teflon, 31 mils, 2 oz. Copper
TYPICAL CHARACTERISTICS, 135 – 175 MHz
Figure 2. Output Power versus Input Power
Figure 3. Input Return Loss
versus Output Power
MRF1511T1
5.2–54 MOTOROLA WIRELESS
RF PRODUCT DEVICE DATA
TYPICAL CHARACTERISTICS, 135 – 175 MHz
Figure 4. Gain versus Output Power
Figure 5. Drain Efficiency versus Output Power
Figure 6. Output Power versus Biasing Current
Figure 7. Drain Efficiency versus
Biasing Current
Figure 8. Output Power versus Supply Voltage
Figure 9. Drain Efficiency versus Supply Voltage
5.2–55
MRF1511T1MOTOROLA WIRELESS
RF PRODUCT DEVICE DATA
Figure 10. 66 – 88 MHz Broadband Test Circuit
B1, B2 Short Ferrite Bead, Fair Rite Products
(2743021446)
C1, C12 330 pF, 100 mil Chip Capacitor
C2 43 pF, 100 mil Chip Capacitor
C3, C10 0 to 20 pF, Trimmer Capacitor
C4 24 pF, 100 mil Chip Capacitor
C5, C16 120 pF, 100 mil Chip Capacitor
C6, C13 10 µF, 50 V Electrolytic Capacitor
C7, C14 1,200 pF, 100 mil Chip Capacitor
C8, C15 0.1 µF, 100 mil Chip Capacitor
C9 380 pF, 100 mil Chip Capacitor
C11 75 pF, 100 mil Chip Capacitor
L1 82 nH, Coilcraft
L2 55.5 nH, 5 Turn, Coilcraft
L3 39 nH, 6 Turn, Coilcraft
N1, N2 Type N Flange Mount
R1 15 Ω, 0805 Chip Resistor
R2 51 Ω, 1/2 W Resistor
R3 100 Ω, 0805 Chip Resistor
R4 33 kΩ, 1/8 W Resistor
Z1 0.136″ x 0.080″ Microstrip
Z2 0.242″ x 0.080″ Microstrip
Z3 1.032″ x 0.080″ Microstrip
Z4 0.145″ x 0.080″ Microstrip
Z5, Z6 0.260″ x 0.223″ Microstrip
Z7 0.134″ x 0.080″ Microstrip
Z8 0.490″ x 0.080″ Microstrip
Z9 0.872″ x 0.080″ Microstrip
Z10 0.206″ x 0.080″ Microstrip
Board Glass Teflon, 31 mils, 2 oz. Copper
TYPICAL CHARACTERISTICS, 66 – 88 MHz
Figure 11. Output Power versus Input Power
Figure 12. Input Return Loss
versus Output Power
MRF1511T1
5.2–56 MOTOROLA WIRELESS
RF PRODUCT DEVICE DATA
TYPICAL CHARACTERISTICS, 66 – 88 MHz
Figure 13. Gain versus Output Power
Figure 14. Drain Efficiency versus
Output Power
Figure 15. Output Power versus
Biasing Current
Figure 16. Drain Efficiency versus
Biasing Current
Figure 17. Output Power versus
Supply Voltage
Figure 18. Drain Efficiency versus
Supply Voltage
5.2–57
MRF1511T1MOTOROLA WIRELESS
RF PRODUCT DEVICE DATA
Note: Z OL* was chosen based on tradeoffs between gain, drain ef ficiency, and device stability.
Figure 19. Series Equivalent Input and Output Impedance
Ω
Zin = Complex conjugate of source
impedance with parallel 15 Ω
resistor and 24 pF capacitor in
series with gate. (See Figure 10).
ZOL* = Complex conjugate of the load
impedance at given output power,
voltage, frequency, and ηD > 50 %.
f
MHz Zin
ΩZOL*
Ω
135 20.1 –j0.5 2.53 –j2.61
Zin = Complex conjugate of source
impedance with parallel 15 Ω
resistor and 68 pF capacitor in
series with gate. (See Figure 1).
ZOL* = Complex conjugate of the load
impedance at given output power,
voltage, frequency, and ηD > 50 %.
155 17.0 +j3.6 3.01 –j2.48
175 15.2 +j7.9 2.52 –j3.02
f
MHz Zin
ΩZOL*
Ω
66 25.3 –j0.31 3.62 –j0.751
77 25.6 +j3.62 3.59 –j0.129
88 26.7 +j6.79 3.37 –j0.173
-68 -"
MRF1511T1
5.2–58 MOTOROLA WIRELESS
RF PRODUCT DEVICE DATA
Table 1. Common Source Scattering Parameters (VDD = 7.5 Vdc)
IDQ = 150 mA
f
S11 S21 S12 S22
f
MHz |S11|∠φ|S21|∠φ|S12|∠φ|S22|∠φ
30 0.88 –165 18.92 95 0.015 8 0.84 –169
50 0.88 –171 11.47 91 0.016 –5 0.84 –173
100 0.87 –175 5.66 85 0.016 –7 0.84 –176
150 0.87 –176 3.75 82 0.015 –5 0.85 –176
200 0.87 –177 2.78 78 0.014 –6 0.84 –176
250 0.87 –177 2.16 75 0.014 –10 0.85 –176
300 0.88 –177 1.77 72 0.012 –17 0.86 –176
350 0.88 –177 1.49 69 0.013 –11 0.86 –176
400 0.88 –177 1.26 66 0.013 –17 0.87 –175
450 0.88 –177 1.08 64 0.011 –20 0.87 –175
500 0.89 –176 0.96 63 0.012 –20 0.88 –175
IDQ = 800 mA
f
S11 S21 S12 S22
f
MHz |S11|∠φ|S21|∠φ|S12|∠φ|S22|∠φ
30 0.89 –166 18.89 95 0.014 10 0.85 –170
50 0.88 –172 11.44 91 0.015 8 0.84 –174
100 0.87 –175 5.65 86 0.016 –2 0.85 –176
150 0.87 –177 3.74 82 0.014 –8 0.84 –177
200 0.87 –177 2.78 78 0.013 –18 0.85 –177
250 0.88 –177 2.16 75 0.012 –11 0.85 –176
300 0.88 –177 1.77 73 0.015 –15 0.86 –176
350 0.88 –177 1.50 70 0.009 –7 0.87 –176
400 0.88 –177 1.26 67 0.012 –3 0.87 –176
450 0.88 –177 1.09 65 0.012 –18 0.87 –175
500 0.89 –177 0.97 64 0.009 –10 0.88 –175
IDQ = 1.5 A
f
S11 S21 S12 S22
f
MHz |S11|∠φ|S21|∠φ|S12|∠φ|S22|∠φ
30 0.90 –168 17.89 95 0.013 2 0.86 –172
50 0.89 –173 10.76 91 0.013 3 0.86 –175
100 0.88 –176 5.32 86 0.014 –19 0.86 –177
150 0.88 –177 3.53 83 0.013 –6 0.86 –177
200 0.88 –177 2.63 80 0.011 –4 0.86 –177
250 0.88 –178 2.05 77 0.012 –14 0.86 –177
300 0.88 –177 1.69 75 0.013 –2 0.87 –177
350 0.89 –177 1.43 72 0.010 –9 0.87 –176
400 0.89 –177 1.22 70 0.014 –3 0.88 –176
450 0.89 –177 1.06 68 0.011 –8 0.88 –176
500 0.89 –177 0.94 67 0.011 –15 0.88 –176
5.2–59
MRF1511T1MOTOROLA WIRELESS
RF PRODUCT DEVICE DATA
APPLICATIONS INFORMATION
DESIGN CONSIDERATIONS
This device is a common–source, RF power, N–Channel
enhancement mode, Lateral Metal–Oxide Semiconductor
Field–Effect Transistor (MOSFET). Motorola Application
Note AN211A, “FETs in Theory and Practice”, is suggested
reading for those not familiar with the construction and char-
acteristics of FETs.
This surface mount packaged device was designed pri-
marily for VHF and UHF portable power amplifier applica-
tions. Manufacturability is improved by utilizing the tape and
reel capability for fully automated pick and placement of
parts. However, care should be taken in the design process
to insure proper heat sinking of the device.
The major advantages of Lateral RF power MOSFETs in-
clude high gain, simple bias systems, relative immunity from
thermal runaway, and the ability to withstand severely mis-
matched loads without suffering damage.
MOSFET CAPACITANCES
The physical structure of a MOSFET results in capacitors
between all three terminals. The metal oxide gate structure
determines the capacitors from gate–to–drain (Cgd), and
gate–to–source (Cgs). The PN junction formed during fab-
rication of the RF MOSFET results in a junction capacitance
from drain–to–source (Cds). These capacitances are charac-
terized as input (Ciss), output (Coss) and reverse transfer
(Crss) capacitances on data sheets. The relationships be-
tween 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 ap-
plications.
DRAIN CHARACTERISTICS
One critical figure of merit for a FET is its static resistance
in the full–on condition. This on–resistance, RDS(on), occurs
in the linear region of the output characteristic and is speci-
fied at a specific gate–source voltage and drain current. The
drain–source voltage under these conditions is termed
VDS(on). For MOSFETs, VDS(on) has a positive temperature
coefficient at high temperatures because it contributes to the
power dissipation within the device.
BVDSS values for this device are higher than normally re-
quired for typical applications. Measurement of BVDSS is not
recommended and may result in possible damage to the de-
vice.
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 DC input resistance is very high – on the order of 109 Ω
— resulting in a leakage current of a few nanoamperes.
Gate control is achieved by applying a positive voltage to
the gate greater than 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–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 protec-
tion is required, an external zener diode is recommended.
Using a resistor to keep the gate–to–source impedance low
also helps dampen 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.
DC BIAS
Since this device is an enhancement mode FET, drain cur-
rent flows only when the gate is at a higher potential than the
source. RF power FETs operate optimally with a quiescent
drain current (IDQ), whose value is application dependent.
This device was characterized at IDQ = 150 mA, which is the
suggested value of bias current for typical applications. 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. There-
fore, the gate bias circuit may generally be just a simple re-
sistive divider network. Some special applications may
require a more elaborate bias system.
GAIN CONTROL
Power output of this device may be controlled to some de-
gree with a low power dc control signal applied to the gate,
thus facilitating applications such as manual gain control,
ALC/AGC and modulation systems. This characteristic is
very dependent on frequency and load line.
MRF1511T1
5.2–60 MOTOROLA WIRELESS
RF PRODUCT DEVICE DATA
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 Motorola 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 Motorola 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
Motorola Application Note AN215A, “RF Small–Signal
Design Using Two–Port Parameters” for a discussion of two
port network theory and stability.
