1
MRF1508 MRF1508T1MOTOROLA RF DEVICE DATA
The RF MOSFET Line
    
N–Channel Enhancement–Mode Lateral MOSFETs
The MRF1508 is designed for broadband commercial and industrial
applications at frequencies to 520 MHz. The high gain and broadband
performance of this device makes it ideal for large–signal, common source
amplifier applications in 12.5 volt mobile FM equipment.
•Specified Performance @ 520 MHz, 12.5 Volts
Output Power — 8 Watts
Power Gain — 14 dB
Efficiency — 60%
•Characterized with Series Equivalent Large–Signal
Impedance Parameters
•Excellent Thermal Stability
•Capable of Handling 20:1 VSWR, @ 15.5 Vdc,
520 MHz, 2 dB Overdrive
•RF Power Plastic Surface Mount Package
•Broadband UHF/VHF Demonstration Amplifier
Information Available Upon Request
•Available in Tape and Reel by Adding T1 Suffix to
Part Number. 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
0.50 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 =
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 MRF1508/D

SEMICONDUCTOR TECHNICAL DATA


8 W, 520 MHz, 12.5 V
LATERAL N–CHANNEL
BROADBAND
RF POWER MOSFET
CASE 466–02, STYLE 1
(PLD 1.5)
PLASTIC
Motorola, Inc. 1998
G
D
S
TJ–T
C
R
θJC
MRF1508 MRF1508T1
2MOTOROLA RF DEVICE DATA
ELECTRICAL CHARACTERISTICS (TC = 25°C unless otherwise noted)
Characteristic Symbol Min Typ Max Unit
OFF CHARACTERISTICS
Zero Gate Voltage Drain Current
(VDS = 40 Vdc, VGS = 0) IDSS — — 10 µAdc
Gate–Source Leakage Current
(VGS = 20 Vdc, VDS = 0) IGSS — — 1 µAdc
ON CHARACTERISTICS
Gate Threshold Voltage
(VDS = 10 Vdc, ID = 100 µA) VGS(th) 2.4 3 — Vdc
Drain–Source On–V oltage
(VGS = 10 Vdc, ID = 2 Adc) VDS(on) 0.3 0.5 — Vdc
Forward T ransconductance
(VDS = 10 Vdc, ID = 2 Adc) gfs 1.3 1.75 — S
DYNAMIC CHARACTERISTICS
Input Capacitance
(VDS = 12.5 Vdc, VGS = 0, f = 1 MHz) Ciss —47 — pF
Output Capacitance
(VDS = 12.5 Vdc, VGS = 0, f = 1 MHz) Coss —35 — pF
Reverse T ransfer Capacitance
(VDS = 12.5 Vdc, VGS = 0, f = 1 MHz) Crss —4.1 — pF
FUNCTIONAL TESTS (In Motorola Test Fixture)
Common–Source Amplifier Power Gain
(VDD = 12.5 Vdc, Pout = 8 W atts, IDQ = 150 mA, f = 520 MHz) Gps 12 14 — dB
Drain Efficiency
(VDD = 12.5 Vdc, Pout = 8 W atts, IDQ = 150 mA, f = 520 MHz) η55 60 — %
3
MRF1508 MRF1508T1MOTOROLA RF DEVICE DATA
Figure 1. 500 – 520 MHz Broadband Test Circuit
B1 Fair Rite Products Long Ferrite Bead
C1, C5 10 µF, 50 V Electrolytic Capacitor
C2, C4 0.1 µF, 100 mil Chip Capacitor
C3, C6, C7, C8 130 pF, 100 mil Chip Capacitor
C9 0.8–8 pF, Variable Capacitor, Gigatrim
C10 0.8–18 pF, Variable Capacitor, Johanson
C11 16 pF, 100 mil Chip Capacitor
C12 0.8–18 pF, Variable Capacitor, Johanson
C13 0.8–8 pF, Variable Capacitor, Gigatrim
L1 4 Turns, #20 AWG Enamel Coil, 0.1″ID
N1, N2 T ype–N Flange Mount Connector
R1 1.1 MΩ, 1/4 W Carbon Resistor
R2 1.0 kΩ, 0.1 W Chip Resistor
R3 1 kΩ, 1/4 W Carbon Resistor
VGG VDD
C1 R1
R2
C2 C3 C5C4 +
R3
RF
INPUT
RF
OUTPUT
Z1 Z2 Z3 Z4
Z7
C7 C9
C8
DUT
Z8
C11
Z10 Z11
Z5 Z6
L1
Z9 N2
C6
B1
N1
Z1, Z13 0.290″ x 0.081″ Microstrip
Z2 0.070″ x 0.217″ Microstrip
Z3 2.950″ x 0.217″ Microstrip
Z4 0.150″ x 0.217″ Microstrip
Z5 0.250″ x 0.217″ Microstrip
Z6 0.250″ x 0.0073″ Microstrip AIO2
Z7 0.250″ x 0.0073″ Microstrip AIO2
Z8 0.050″ x 0.217″ Microstrip
Z9 0.100″ x 0.217″ Microstrip
Z10 0.150″ x 0.217″ Microstrip
Z11 1.500″ x 0.217″ Microstrip
Z12 1.550″ x 0.217″ Microstrip
Board Glass Teflon, 31 mils, 2 oz. Copper
+
C13
Z12 Z13
C10
C12
TYPICAL CHARACTERISTICS
Pout, OUTPUT POWER (W ATTS)
IRL, INPUT RETURN LOSS (dB)
20
5
010
10
6120
15
25
14842
510 MHz
520 MHz
500 MHz
Figure 2. Output Power versus Input Power
9
Pin, INPUT POWER (WATTS)
1
0.35
5
Figure 3. Input Return Loss
versus Output Power
0.15
P
out, OUTPUT POWER (WATTS)
0
7
11
3
0.250.05 0.45
8
4
6
10
2
520 MHz 510 MHz
500 MHz
0.400.20 0.300.10
0
12
13
MRF1508 MRF1508T1
4MOTOROLA RF DEVICE DATA
TYPICAL CHARACTERISTICS
10 4
Pout, OUTPUT POWER (W ATTS)
90
50
20
70
014
Eff, DRAIN EFFICIENCY (%)
8
30
60
80
12
40
6210
500 MHz
520 MHz
510 MHz
500 MHz
Eff, DRAIN EFFICIENCY (%)
Figure 4. Gain versus Output Power
18
Pout, OUTPUT POWER (W ATTS)
11
10 8
14
16
Figure 5. Drain Efficiency versus Output Power
412
GAIN (dB)
0
17
Figure 6. Output Power versus Biasing Current
15
IDQ, BIASING CURRENT (mA)
3
Figure 7. Drain Efficiency versus
Biasing Current
70
IDQ, BIASING CURRENT (mA)
45
700
Figure 8. Output Power versus Supply Voltage
8VDD, SUPPLY VOLTAGE (VOLTS)
215
Figure 9. Drain Efficiency versus Supply Voltage
VDD, SUPPLY VOLTAGE (VOLTS)
30 12
11 8
0
45
60
60
40 400 5000
10
18
20
600 700 800
80
80
5
7
9
11
12
15
13
200
50
14
13
P
out, OUTPUT POWER (W ATTS)
100 200 300 800400 500 600
VDD = 12.5 V
Pin = 27 dBm
P
out, OUTPUT POWER (WATTS)
9121310 14 16
IDQ = 150 mA
Pin = 27 dBm
91011 1413 16
19
1062
520 MHz 510 MHz
500 MHz
500 MHz
510 MHz
520 MHz
VDD = 12.5 V
Pin = 27 dBm
100 300
75
65
55
520 MHz
500 MHz 510 MHz
4
6
8
12
14
16
Eff, DRAIN EFFICIENCY (%)
15
35
50
65
70
40
55
75
500 MHz 510 MHz
520 MHz
IDQ = 150 mA
Pin = 27 dBm
510 MHz
520 MHz
5
MRF1508 MRF1508T1MOTOROLA RF DEVICE DATA
Figure 10. 400 – 470 MHz Broadband Test Circuit
B1 Fair Rite Products Long Ferrite Bead
C1, C5 10 µF, 50 V Electrolytic Capacitor
C2, C4 0.1 µF, 100 mil Chip Capacitor
C3, C6, C7, C8 130 pF, 100 mil Chip Capacitor
C9 10 pF, 100 mil Chip Capacitor
C10 0.8–8 pF, Variable Capacitor, Gigatrim
C11 47 pF, 100 mil Chip Capacitor
C12 16 pF, 100 mil Chip Capacitor
C13 6.2 pF, 100 mil Chip Capacitor
C14 5.1 pF, 100 mil Chip Capacitor
L1 4 Turns, #20 AWG Enamel Coil, 0.1″ID
N1, N2 T ype–N Flange Mount Connector
R1 1.1 MΩ, 1/4 W Carbon Resistor
R2 1.0 kΩ, 0.1 W Chip Resistor
VGG VDD
C1 R1
R2
C2 C3 C5C4 +
R3
RF
INPUT
RF
OUTPUT
Z1 Z2 Z3 Z4
Z8
C7 C10
C8
DUT
Z9 Z10 Z11
Z5 Z6
L1
N2
C6
B1
N1
R3 1 kΩ, 1/4 W Carbon Resistor
Z1, Z13 0.290″ x 0.081″ Microstrip
Z2 0.150″ x 0.217″ Microstrip
Z3 2.650″ x 0.217″ Microstrip
Z4 0.200″ x 0.217″ Microstrip
Z5 0.300″ x 0.217″ Microstrip
Z6 0.050″ x 0.217″ Microstrip
Z7, Z8 0.313″ x 0.160″ Microstrip
Z9 0.200″ x 0.217″ Microstrip
Z10 0.800″ x 0.217″ Microstrip
Z11 2.400″ x 0.217″ Microstrip
Z12 0.100″ x 0.217″ Microstrip
Board Glass Teflon, 31 mils, 2 oz. Copper
Insert Glass Teflon, 31 mils, 2 oz. Copper
+
C14
Z12 Z13
C11
C13
C12
C9
Z7
TYPICAL CHARACTERISTICS
Pout, OUTPUT POWER (W ATTS)
IRL, INPUT RETURN LOSS (dB)
–4
–16
–20 10
–12
6120
–8
0
14842
Figure 11. Output Power versus Input Power
Pin, INPUT POWER (MILLIW ATTS)
Figure 12. Input Return Loss
versus Output Power
600
P
out, OUTPUT POWER (WATTS)
0 200 1000
8
4
6
10
2
470 MHz 400 MHz
440 MHz
800400
0
12
14
470 MHz
400 MHz
440 MHz
–6
–18
–14
–10
–2
MRF1508 MRF1508T1
6MOTOROLA RF DEVICE DATA
TYPICAL CHARACTERISTICS
400 MHz
04
Pout, OUTPUT POWER (W ATTS)
40
10
60
014
Eff, DRAIN EFFICIENCY (%)
8
20
50
70
12
30
6210
Eff, DRAIN EFFICIENCY (%)
Figure 13. Gain versus Output Power
18
Pout, OUTPUT POWER (W ATTS)
68
14
16
Figure 14. Drain Efficiency versus Output Power
412
GAIN (dB)
0
Figure 15. Output Power versus Biasing Current
18
IDQ, BIASING CURRENT (mA)
2
Figure 16. Drain Efficiency versus
Biasing Current
70
IDQ, BIASING CURRENT (mA)
20
700
Figure 17. Output Power versus Supply Voltage
6VDD, SUPPLY VOLTAGE (VOLTS)
214
Figure 18. Drain Efficiency versus Supply Voltage
VDD, SUPPLY VOLTAGE (VOLTS)
10 13
96
0
40
70
50
10 400 5000
10
18
20
600 700 800
90
90
14
10
16
200
30
14
P
out, OUTPUT POWER (W ATTS)
100 200 300 800400 500 600
VDD = 12.5 V
Pin = 27 dBm
P
out, OUTPUT POWER (WATTS)
7101181216
I
DQ = 150 mA
Pin = 27 dBm
810121416
1062
VDD = 12.5 V
Pin = 27 dBm
100 300
80
60
40
4
6
8
12
14
16
Eff, DRAIN EFFICIENCY (%)
15
20
50
80
30
60
470 MHz 440 MHz 400 MHz
470 MHz
440 MHz
12
8
10
4
6
440 MHz
470 MHz
400 MHz 470 MHz
400 MHz
440 MHz
1513
440 MHz
470 MHz
400 MHz
IDQ = 150 mA
Pin = 27 dBm
7911
470 MHz
400 MHz
440 MHz
12
8
7
MRF1508 MRF1508T1MOTOROLA RF DEVICE DATA
Figure 19. 136 – 175 MHz Broadband Test Circuit
B1 Fair Rite Products Long Ferrite Bead
C1, C5 10 µF, 50 V Electrolytic Capacitor
C2, C4 0.1 µF, 100 mil Chip Capacitor
C3, C6, C7, C8 130 pF, 100 mil Chip Capacitor
C9 82 pF, 100 mil Chip Capacitor
C10 6.2 pF, 100 mil Chip Capacitor
C11 30 pF, 100 mil Chip Capacitor
C12 75 pF, 100 mil Chip Capacitor
C13 39 pF, 100 mil Chip Capacitor
L1 4 Turns, #20 AWG Enamel Coil, 0.1″ID
L2 17.5 nH Air Core Inductor, Coilcraft A06T
L3 22 nH Air Core Inductor, Coilcraft A07T
L4 18.5 nH Air Core Inductor, Coilcraft A05T
L5 5 nH Air Core Inductor, Coilcraft A02T
N1, N2 T ype–N Flange Mount Connector
R1 1.1 MΩ, 1/4 W Carbon Resistor
R2 1.0 kΩ, 0.1 W Chip Resistor
VGG VDD
C1 R1
R2
C2 C3 C5C4 +
R3
RF
INPUT
RF
OUTPUT
Z1 Z2 Z3 Z4
C7 C10
C8
C11
DUT
Z10 Z11
R4
C9
Z5 Z6
L1
N2
C6
B1
N1
R3 50 Ω, 1/4 W Carbon Resistor
R4 20 Ω, 0.1 W Chip Resistor
Z1 0.200″ x 0.081″ Microstrip
Z2 0.050″ x 0.081″ Microstrip
Z3 0.450″ x 0.081″ Microstrip
Z4 0.050″ x 0.081″ Microstrip
Z5 0.550″ x 0.081″ Microstrip
Z6 0.350″ x 0.081″ Microstrip
Z7 1.150″ x 0.081″ Microstrip
Z8 0.250″ x 0.081″ Microstrip
Z9 0.350″ x 0.081″ Microstrip
Z10 0.500″ x 0.081″ Microstrip
Z11 1.150″ x 0.081″ Microstrip
Z12 1.450″ x 0.081″ Microstrip
Z13 0.050″ x 0.081″ Microstrip
Z14 0.200″ x 0.081″ Microstrip
Board Glass Teflon, 31 mils, 2 oz. Copper
+
C13
Z13 Z14
L2
C12
Z9Z7 Z8
Z12
L3 L4
L5
TYPICAL CHARACTERISTICS
Pout, OUTPUT POWER (W ATTS)
IRL, INPUT RETURN LOSS (dB)
–4
–16
–20 10
–12
6120
–8
0
14842
Figure 20. Output Power versus Input Power
Pin, INPUT POWER (MILLIW ATTS)
Figure 21. Input Return Loss
versus Output Power
600
P
out, OUTPUT POWER (WATTS)
0 200 1000
8
4
6
10
2
136 MHz
175 MHz
155 MHz
800400
0
12
14
–6
–18
–14
–10
–2
155 MHz
136 MHz
175 MHz
MRF1508 MRF1508T1
8MOTOROLA RF DEVICE DATA
TYPICAL CHARACTERISTICS
10 4
Pout, OUTPUT POWER (W ATTS)
90
50
20
70
014
Eff, DRAIN EFFICIENCY (%)
8
30
60
80
12
40
6210
Eff, DRAIN EFFICIENCY (%)
Figure 22. Gain versus Output Power
Pout, OUTPUT POWER (W ATTS)
5
08
20
Figure 23. Drain Efficiency versus Output Power
412
GAIN (dB)
0
Figure 24. Output Power versus Biasing Current
20
IDQ, BIASING CURRENT (mA)
2
Figure 25. Drain Efficiency versus
Biasing Current
70
IDQ, BIASING CURRENT (mA)
20
700
Figure 26. Output Power versus Supply Voltage
6VDD, SUPPLY VOLTAGE (VOLTS)
214
Figure 27. Drain Efficiency versus Supply Voltage
VDD, SUPPLY VOLTAGE (VOLTS)
10 10
96
0
40
70
50
10 400 5000
10
20
30
600 700 800
90
90
4
6
10
14
10
25
200
30
14
15
P
out, OUTPUT POWER (W ATTS)
100 200 300 800400 500 600
VDD = 12.5 V
Pin = 27 dBm
P
out, OUTPUT POWER (WATTS)
7101181216
I
DQ = 150 mA
Pin = 27 dBm
789 1211 16
1062
VDD = 12.5 V
Pin = 27 dBm
100 300
80
60
40
4
6
8
12
14
16
Eff, DRAIN EFFICIENCY (%)
14
20
50
30
60
80
IDQ = 150 mA
Pin = 27 dBm
155 MHz
136 MHz
175 MHz
155 MHz
175 MHz
136 MHz
18
8
12
16
155 MHz
136 MHz
175 MHz
175 MHz
155 MHz
136 MHz
18
1513
155 MHz
175 MHz
136 MHz
13 15
175 MHz
155 MHz
136 MHz
9
MRF1508 MRF1508T1MOTOROLA RF DEVICE DATA
f
MHz Zin
ΩZOL*
Ω
135 11.7 – j4.4 8.7 – j0.2
Zin = Conjugate of source impedance
with parallel 20 Ω resistor and
82 pF capacitor in series with gate.
(See Figure 19).
ZOL* = Conjugate of the load impedance
at given output power, voltage,
frequency, and ηD > 50 %.
VDD = 12.5 V, IDQ = 150 mA, Pout = 8 W
155 11.8 – j6.8 7.2 – j3.8
Note: ZOL* was chosen based on tradeoffs between gain, drain efficiency , and device stability.
Zin
ZOL*
Figure 28. Series Equivalent Input and Output Impedance
175 11.3 – j8.8 6.3 – j7.7
Zo = 10
Ω
f = 500 MHz
520
f
MHz Zin
ΩZOL*
Ω
400 2.5 – j3.9 7.1 – j0.1
Zin = Conjugate of source impedance
with parallel 20 Ω resistor and
82 pF capacitor in series with gate.
(See Figure 10).
ZOL* = Conjugate of the load impedance
at given output power, voltage,
frequency, and ηD > 50 %.
VDD = 12.5 V, IDQ = 150 mA, Pout = 8 W
440 3.0 – j4.1 6.8 – j2.3
470 2.4 – j4.3 6.8 – j4.2
f
MHz Zin
ΩZOL*
Ω
500 2.0 – j4.8 3.5 – j3.5
Zin = Conjugate of source impedance
with parallel 20 Ω resistor and
82 pF capacitor in series with gate.
(See Figure 1).
ZOL* = Conjugate of the load impedance
at given output power, voltage,
frequency, and ηD > 50 %.
VDD = 12.5 V, IDQ = 150 mA, Pout = 8 W
510 2.4 – j3.4 3.5 – j2.7
520 2.2 – j3.8 3.5 – j2.6
ZOL*Zin
ZOL*
f = 500 MHz
520
470
400
Zin
470
f = 400 MHz
f = 135 MHz
175
f = 135 MHz
175
MRF1508 MRF1508T1
10 MOTOROLA RF DEVICE DATA
Table 1. Common Source Scattering Parameters (VDS = 12.5 Vdc, IDQ = 150 mA)
fS11 S21 S12 S22
f
MHz |S11|∠φ|S21|∠φ|S12|∠φ|S22|∠φ
50 0.770 –136 16.04 101 0.040 12 0.670 –137
100 0.760 –154 8.15 86 0.040 –3 0.680 –153
150 0.770 –160 5.30 77 0.040 –11 0.700 –158
200 0.780 –163 3.83 70 0.040 –18 0.720 –160
250 0.800 –165 2.91 64 0.040 –23 0.750 –161
300 0.820 –166 2.29 58 0.030 –27 0.780 –162
350 0.840 –167 1.87 54 0.030 –31 0.800 –163
400 0.850 –168 1.54 50 0.030 –35 0.820 –164
450 0.860 –168 1.29 47 0.030 –38 0.840 –165
500 0.870 –169 1.09 44 0.030 –39 0.850 –166
550 0.880 –170 0.96 41 0.020 –42 0.870 –166
600 0.890 –170 0.83 39 0.020 –43 0.880 –167
650 0.900 –171 0.72 37 0.020 –44 0.890 –168
700 0.910 –171 0.65 35 0.020 –44 0.890 –168
750 0.910 –172 0.59 32 0.020 –45 0.900 –169
800 0.920 –172 0.52 30 0.020 –48 0.910 –169
850 0.930 –173 0.46 29 0.020 –50 0.910 –170
900 0.930 –173 0.42 28 0.010 –51 0.920 –170
950 0.930 –173 0.38 26 0.010 –54 0.920 –170
1000 0.930 –173 0.35 24 0.010 –52 0.920 –171
1050 0.930 –174 0.31 23 0.010 –51 0.930 –171
1100 0.930 –174 0.28 22 0.010 –45 0.930 –171
1150 0.940 –174 0.26 21 0.010 –53 0.930 –172
1200 0.940 –174 0.24 21 0.010 –60 0.930 –172
11
MRF1508 MRF1508T1MOTOROLA RF DEVICE DATA
Table 2. Common Source Scattering Parameters (VDS = 12.5 Vdc, IDQ = 800 mA)
fS11 S21 S12 S22
f
MHz |S11|∠φ|S21|∠φ|S12|∠φ|S22|∠φ
50 0.840 –152 19.13 99 0.020 10 0.740 –158
100 0.820 –165 9.60 88 0.020 0 0.760 –167
150 0.820 –169 6.33 82 0.020 –6 0.760 –170
200 0.830 –171 4.68 77 0.020 –10 0.770 –170
250 0.830 –172 3.64 73 0.020 –13 0.780 –171
300 0.840 –172 2.94 69 0.020 –15 0.790 –171
350 0.850 –173 2.48 66 0.020 –18 0.800 –171
400 0.850 –173 2.09 62 0.020 –21 0.810 –171
450 0.860 –173 1.80 60 0.020 –22 0.820 –170
500 0.870 –174 1.56 57 0.020 –24 0.830 –171
550 0.870 –174 1.39 54 0.020 –25 0.840 –171
600 0.880 –174 1.23 52 0.020 –27 0.850 –171
650 0.880 –174 1.09 50 0.020 –26 0.860 –171
700 0.890 –174 1.00 48 0.010 –28 0.860 –171
750 0.900 –174 0.91 45 0.010 –29 0.870 –172
800 0.900 –174 0.82 43 0.010 –31 0.870 –172
850 0.910 –175 0.74 41 0.010 –32 0.880 –172
900 0.910 –175 0.68 40 0.010 –32 0.880 –172
950 0.910 –175 0.62 37 0.010 –36 0.880 –172
1000 0.910 –175 0.56 36 0.010 –33 0.880 –173
1050 0.920 –175 0.51 34 0.010 –35 0.880 –172
1100 0.920 –175 0.46 33 0.010 –25 0.890 –173
1150 0.920 –175 0.43 33 0.010 –34 0.880 –173
1200 0.920 –175 0.39 32 0.010 –40 0.880 –173
MRF1508 MRF1508T1
12 MOTOROLA RF DEVICE DATA
Table 3. Common Source Scattering Parameters (VDS = 12.5 Vdc, IDQ = 1.5 mA)
fS11 S21 S12 S22
f
MHz |S11|∠φ|S21|∠φ|S12|∠φ|S22|∠φ
50 0.860 –152 18.90 100 0.020 11 0.740 –160
100 0.830 –165 9.46 89 0.020 1 0.770 –168
150 0.830 –169 6.24 83 0.020 –4 0.770 –171
200 0.840 –171 4.61 78 0.020 –9 0.780 –171
250 0.840 –172 3.59 74 0.020 –12 0.790 –171
300 0.840 –173 2.91 70 0.020 –15 0.800 –171
350 0.850 –173 2.45 67 0.020 –17 0.810 –171
400 0.860 –174 2.07 63 0.020 –20 0.820 –171
450 0.860 –174 1.78 60 0.020 –21 0.820 –171
500 0.870 –174 1.55 58 0.020 –22 0.840 –171
550 0.880 –174 1.39 55 0.020 –24 0.840 –171
600 0.880 –174 1.23 53 0.020 –24 0.850 –171
650 0.890 –175 1.09 51 0.010 –24 0.860 –172
700 0.890 –175 1.00 49 0.010 –25 0.860 –172
750 0.900 –175 0.91 46 0.010 –27 0.870 –172
800 0.900 –175 0.82 43 0.010 –28 0.870 –172
850 0.910 –175 0.74 42 0.010 –31 0.870 –173
900 0.910 –175 0.68 40 0.010 –30 0.870 –173
950 0.910 –175 0.62 38 0.010 –32 0.870 –173
1000 0.910 –175 0.56 36 0.010 –31 0.860 –173
1050 0.920 –175 0.51 35 0.010 –29 0.860 –173
1100 0.920 –175 0.46 34 0.010 –22 0.860 –173
1150 0.920 –175 0.43 34 0.010 –30 0.850 –173
1200 0.920 –175 0.39 33 0.010 –35 0.850 –172
13
MRF1508 MRF1508T1MOTOROLA RF DEVICE DATA
APPLICATIONS INFORMATION
DESIGN CONSIDERATIONS
The MRF1508 is a common–source, RF power, N–Channel
enhancement mode, Lateral Metal–Oxide Semiconductor
Field–Effect T ransistor (MOSFET). Motorola Application Note
AN21 1A, “FETs in Theory and Practice”, is suggested reading
for those not familiar with the construction and characteristics
of FETs.
This surface mount packaged device was designed primari-
ly for VHF and UHF portable power amplifier applications.
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
include high gain, simple bias systems, relative immunity from
thermal runaway, and the ability to withstand severely
mismatched 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 fabrica-
tion 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.
Drain
Cds
Source
Gate
Cgd
Cgs
Ciss = Cgd + Cgs
Coss = Cgd + Cds
Crss = Cgd
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 specified
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
required for typical applications. Measurement of BVDSS is not
recommended and may result in possible damage to 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
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
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 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. V oltage 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 the MRF1508 is an enhancement mode FET, drain
current flows only when the gate is at a higher potential than
the source. RF power FET s operate optimally with a quiescent
drain current (IDQ), whose value is application dependent. The
MRF1508 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.
Therefore, the gate bias circuit may generally be just a simple
resistive divider network. Some special applications may
require a more elaborate bias system.
GAIN CONTROL
Power output of the MRF1508 may be controlled to some
degree 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.
MRF1508 MRF1508T1
14 MOTOROLA RF DEVICE DATA
MOUNTING
The specified maximum thermal resistance of 2°C/W
assumes a majority of the 0.065″ x 0.180″ source contact on
the back side of the package is in good contact with an
appropriate 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 Method 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 information.
AMPLIFIER DESIGN
Impedance matching networks similar to those used with
bipolar transistors are suitable for the MRF1508. 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 the
MRF1508 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 fixture implements a parallel resistor and capacitor in
series with the gate, and has a load line selected for a higher
efficiency, lower gain, and more stable operating region.
Two–port stability analysis with the MRF1508
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.
15
MRF1508 MRF1508T1MOTOROLA RF DEVICE DATA
PACKAGE DIMENSIONS
CASE 466–02
ISSUE B
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH
3. RESIN BLEED/FLASH ALLOWABLE IN ZONE V, W,
AND X.
_
DIM MIN MAX MIN MAX
MILLIMETERSINCHES
A0.255 0.265 6.48 6.73
B0.225 0.235 5.72 5.97
C0.065 0.072 1.65 1.83
D0.130 0.150 3.30 3.81
E0.021 0.026 0.53 0.66
F0.026 0.044 0.66 1.12
G0.050 0.070 1.27 1.78
H0.045 0.063 1.14 1.60
K0.273 0.285 6.93 7.24
L0.245 0.255 6.22 6.48
N0.230 0.240 5.84 6.10
P0.000 0.008 0.00 0.20
Q0.055 0.063 1.40 1.60
R0.200 0.210 5.08 5.33
S0.006 0.012 0.15 0.31
U0.006 0.012 0.15 0.31
ZONE V 0.000 0.021 0.00 0.53
ZONE W 0.000 0.010 0.00 0.25
ZONE X 0.000 0.010 0.00 0.25
STYLE 1:
PIN 1. DRAIN
2. GATE
3. SOURCE
4. SOURCE
2
34
1
AF
R
L
NK
D
B
Q
E
PC
ÉÉÉÉ
ÉÉÉÉ
ÉÉÉÉ
ÉÉÉÉ
ÉÉÉÉ
ÉÉÉÉ
G
H
ZONE X
ZONE W
0.89 (0.035) X 45 5
"
_
_
10 DRAFT
ZONE V
S
U
ÉÉÉ
ÉÉÉ
RESIN BLEED/FLASH ALLOWABLE
J0.160 0.180 4.06 4.57
J
MRF1508 MRF1508T1
16 MOTOROLA RF DEVICE DATA
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. “Typical” parameters which may be provided in Motorola
data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals”
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.
Mfax is a trademark of Motorola, Inc.
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