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  lifetime buy last order 30jun02 last ship 30dec0 2 1 MRF1508 motorola rf device data the rf mosfet line   
  nchannel enhancementmode 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 largesignal, common source amplifier applications in 12.5 volt mobile fm equipment. ? specified performance @ 520 mhz, 12.5 volts output power e 8 watts power gain e 14 db efficiency e 60% ? characterized with series equivalent largesignal 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 drainsource voltage v dss 40 vdc gatesource voltage v gs 20 vdc drain current e continuous i d 4 adc total device dissipation @ t c = 25 c (1) derate above 25 c p d 62.5 0.50 watts w/ c storage temperature range t stg 65 to +150 c operating junction temperature t j 150 c thermal characteristics characteristic symbol max unit thermal resistance, junction to case r q jc 2 c/w (1) calculated based on the formula p d = 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 nchannel broadband rf power mosfet case 46602, style 1 (pld 1.5) plastic ? motorola, inc. 1998 g d s t j t c r q jc rev 1
lifetime buy last order 30jun02 last ship 30dec0 2 MRF1508 2 motorola rf device data electrical characteristics (t c = 25 c unless otherwise noted) characteristic symbol min typ max unit off characteristics zero gate voltage drain current (v ds = 40 vdc, v gs = 0) i dss e e 10 m adc gatesource leakage current (v gs = 20 vdc, v ds = 0) i gss e e 1 m adc on characteristics gate threshold voltage (v ds = 10 vdc, i d = 100 m a) v gs(th) 2.4 3 e vdc drainsource onvoltage (v gs = 10 vdc, i d = 2 adc) v ds(on) 0.3 0.5 e vdc forward transconductance (v ds = 10 vdc, i d = 2 adc) g fs 1.3 1.75 e s dynamic characteristics input capacitance (v ds = 12.5 vdc, v gs = 0, f = 1 mhz) c iss e 47 e pf output capacitance (v ds = 12.5 vdc, v gs = 0, f = 1 mhz) c oss e 35 e pf reverse transfer capacitance (v ds = 12.5 vdc, v gs = 0, f = 1 mhz) c rss e 4.1 e pf functional tests (in motorola test fixture) commonsource amplifier power gain (v dd = 12.5 vdc, p out = 8 watts, i dq = 150 ma, f = 520 mhz) g ps 12 14 e db drain efficiency (v dd = 12.5 vdc, p out = 8 watts, i dq = 150 ma, f = 520 mhz) h 55 60 e %
lifetime buy last order 30jun02 last ship 30dec0 2 3 MRF1508 motorola rf device data figure 1. 500 520 mhz broadband test circuit b1 fair rite products long ferrite bead c1, c5 10 m f, 50 v electrolytic capacitor c2, c4 0.1 m f, 100 mil chip capacitor c3, c6, c7, c8 130 pf, 100 mil chip capacitor c9 0.88 pf, variable capacitor, gigatrim c10 0.818 pf, variable capacitor, johanson c11 16 pf, 100 mil chip capacitor c12 0.818 pf, variable capacitor, johanson c13 0.88 pf, variable capacitor, gigatrim l1 4 turns, #20 awg enamel coil, 0.1 id n1, n2 typen flange mount connector r1 1.1 m w , 1/4 w carbon resistor r2 1.0 k w , 0.1 w chip resistor r3 1 k w , 1/4 w carbon resistor v gg v dd c1 r1 r2 c2 c3 c5 c4 + 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 p out , output power (watts) irl, input return loss (db) 20 5 0 10 10 612 0 15 25 14 8 4 2 510 mhz 520 mhz 500 mhz figure 2. output power versus input power 9 p in , 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 0.25 0.05 0.45 8 4 6 10 2 520 mhz 510 mhz 500 mhz 0.40 0.20 0.30 0.10 0 12 13
lifetime buy last order 30jun02 last ship 30dec0 2 MRF1508 4 motorola rf device data typical characteristics 10 4 p out , output power (watts) 90 50 20 70 014 eff, drain efficiency (%) 8 30 60 80 12 40 6 210 500 mhz 520 mhz 510 mhz 500 mhz eff, drain efficiency (%) figure 4. gain versus output power 18 p out , output power (watts) 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 i dq , biasing current (ma) 3 figure 7. drain efficiency versus biasing current 70 i dq , biasing current (ma) 45 700 figure 8. output power versus supply voltage 8 v dd , supply voltage (volts) 2 15 figure 9. drain efficiency versus supply voltage v dd , supply voltage (volts) 30 12 11 8 0 45 60 60 40 400 500 0 10 18 20 600 700 800 80 80 5 7 9 11 12 15 13 200 50 14 13 p out , output power (watts) 100 200 300 800 400 500 600 v dd = 12.5 v p in = 27 dbm p out , output power (watts) 91213 10 14 16 i dq = 150 ma p in = 27 dbm 91011 14 13 16 19 10 6 2 520 mhz 510 mhz 500 mhz 500 mhz 510 mhz 520 mhz v dd = 12.5 v p in = 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 i dq = 150 ma p in = 27 dbm 510 mhz 520 mhz
lifetime buy last order 30jun02 last ship 30dec0 2 5 MRF1508 motorola rf device data figure 10. 400 470 mhz broadband test circuit b1 fair rite products long ferrite bead c1, c5 10 m f, 50 v electrolytic capacitor c2, c4 0.1 m f, 100 mil chip capacitor c3, c6, c7, c8 130 pf, 100 mil chip capacitor c9 10 pf, 100 mil chip capacitor c10 0.88 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 typen flange mount connector r1 1.1 m w , 1/4 w carbon resistor r2 1.0 k w , 0.1 w chip resistor v gg v dd c1 r1 r2 c2 c3 c5 c4 + 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 k w , 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 p out , output power (watts) irl, input return loss (db) 4 16 20 10 12 612 0 8 0 14 8 4 2 figure 11. output power versus input power p in , input power (milliwatts) 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 800 400 0 12 14 470 mhz 400 mhz 440 mhz 6 18 14 10 2
lifetime buy last order 30jun02 last ship 30dec0 2 MRF1508 6 motorola rf device data typical characteristics 400 mhz 0 4 p out , output power (watts) 40 10 60 014 eff, drain efficiency (%) 8 20 50 70 12 30 6 210 eff, drain efficiency (%) figure 13. gain versus output power 18 p out , output power (watts) 6 8 14 16 figure 14. drain efficiency versus output power 412 gain (db) 0 figure 15. output power versus biasing current 18 i dq , biasing current (ma) 2 figure 16. drain efficiency versus biasing current 70 i dq , biasing current (ma) 20 700 figure 17. output power versus supply voltage 6 v dd , supply voltage (volts) 2 14 figure 18. drain efficiency versus supply voltage v dd , supply voltage (volts) 10 13 9 6 0 40 70 50 10 400 500 0 10 18 20 600 700 800 90 90 14 10 16 200 30 14 p out , output power (watts) 100 200 300 800 400 500 600 v dd = 12.5 v p in = 27 dbm p out , output power (watts) 71011 81216 i dq = 150 ma p in = 27 dbm 810121416 10 6 2 v dd = 12.5 v p in = 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 15 13 440 mhz 470 mhz 400 mhz i dq = 150 ma p in = 27 dbm 7911 470 mhz 400 mhz 440 mhz 12 8
lifetime buy last order 30jun02 last ship 30dec0 2 7 MRF1508 motorola rf device data figure 19. 136 175 mhz broadband test circuit b1 fair rite products long ferrite bead c1, c5 10 m f, 50 v electrolytic capacitor c2, c4 0.1 m f, 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 typen flange mount connector r1 1.1 m w , 1/4 w carbon resistor r2 1.0 k w , 0.1 w chip resistor v gg v dd c1 r1 r2 c2 c3 c5 c4 + 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 w , 1/4 w carbon resistor r4 20 w , 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 z9 z7 z8 z12 l3 l4 l5 typical characteristics p out , output power (watts) irl, input return loss (db) 4 16 20 10 12 612 0 8 0 14 8 4 2 figure 20. output power versus input power p in , input power (milliwatts) 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 800 400 0 12 14 6 18 14 10 2 155 mhz 136 mhz 175 mhz
lifetime buy last order 30jun02 last ship 30dec0 2 MRF1508 8 motorola rf device data typical characteristics 10 4 p out , output power (watts) 90 50 20 70 014 eff, drain efficiency (%) 8 30 60 80 12 40 6 210 eff, drain efficiency (%) figure 22. gain versus output power p out , output power (watts) 5 0 8 20 figure 23. drain efficiency versus output power 412 gain (db) 0 figure 24. output power versus biasing current 20 i dq , biasing current (ma) 2 figure 25. drain efficiency versus biasing current 70 i dq , biasing current (ma) 20 700 figure 26. output power versus supply voltage 6 v dd , supply voltage (volts) 2 14 figure 27. drain efficiency versus supply voltage v dd , supply voltage (volts) 10 10 9 6 0 40 70 50 10 400 500 0 10 20 30 600 700 800 90 90 4 6 10 14 10 25 200 30 14 15 p out , output power (watts) 100 200 300 800 400 500 600 v dd = 12.5 v p in = 27 dbm p out , output power (watts) 71011 81216 i dq = 150 ma p in = 27 dbm 789 12 11 16 10 6 2 v dd = 12.5 v p in = 27 dbm 100 300 80 60 40 4 6 8 12 14 16 eff, drain efficiency (%) 14 20 50 30 60 80 i dq = 150 ma p in = 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 15 13 155 mhz 175 mhz 136 mhz 13 15 175 mhz 155 mhz 136 mhz
lifetime buy last order 30jun02 last ship 30dec0 2 9 MRF1508 motorola rf device data f mhz z in w z ol * w 135 11.7 j4.4 8.7 j0.2 z in = conjugate of source impedance with parallel 20 w resistor and 82 pf capacitor in series with gate. (see figure 19). z ol * = conjugate of the load impedance at given output power, voltage, frequency, and h d > 50 %. v dd = 12.5 v, i dq = 150 ma, p out = 8 w 155 11.8 j6.8 7.2 j3.8 note: z ol * was chosen based on tradeoffs between gain, drain efficiency, and device stability. z in z ol * figure 28. series equivalent input and output impedance 175 11.3 j8.8 6.3 j7.7 z o = 10 w f = 500 mhz 520 f mhz z in w z ol * w 400 2.5 j3.9 7.1 j0.1 z in = conjugate of source impedance with parallel 20 w resistor and 82 pf capacitor in series with gate. (see figure 10). z ol * = conjugate of the load impedance at given output power, voltage, frequency, and h d > 50 %. v dd = 12.5 v, i dq = 150 ma, p out = 8 w 440 3.0 j4.1 6.8 j2.3 470 2.4 j4.3 6.8 j4.2 f mhz z in w z ol * w 500 2.0 j4.8 3.5 j3.5 z in = conjugate of source impedance with parallel 20 w resistor and 82 pf capacitor in series with gate. (see figure 1). z ol * = conjugate of the load impedance at given output power, voltage, frequency, and h d > 50 %. v dd = 12.5 v, i dq = 150 ma, p out = 8 w 510 2.4 j3.4 3.5 j2.7 520 2.2 j3.8 3.5 j2.6 z ol * z in z ol * f = 500 mhz 520 470 400 z in 470 f = 400 mhz f = 135 mhz 175 f = 135 mhz 175
lifetime buy last order 30jun02 last ship 30dec0 2 MRF1508 10 motorola rf device data table 1. common source scattering parameters (v ds = 12.5 vdc, i dq = 150 ma) f s 11 s 21 s 12 s 22 f mhz |s 11 | f |s 21 | f |s 12 | f |s 22 | f 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
lifetime buy last order 30jun02 last ship 30dec0 2 11 MRF1508 motorola rf device data table 2. common source scattering parameters (v ds = 12.5 vdc, i dq = 800 ma) f s 11 s 21 s 12 s 22 f mhz |s 11 | f |s 21 | f |s 12 | f |s 22 | f 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
lifetime buy last order 30jun02 last ship 30dec0 2 MRF1508 12 motorola rf device data table 3. common source scattering parameters (v ds = 12.5 vdc, i dq = 1.5 a) f s 11 s 21 s 12 s 22 f mhz |s 11 | f |s 21 | f |s 12 | f |s 22 | f 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
lifetime buy last order 30jun02 last ship 30dec0 2 13 MRF1508 motorola rf device data applications information design considerations the MRF1508 is a commonsource, rf power, nchannel enhancement mode, lateral m etalo xide s emiconductor f ielde ffect t ransistor (mosfet). motorola application note an211a, afets in theory and practiceo, 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 gatetodrain (c gd ), and gatetosource (c gs ). the pn junction formed during fabrica- tion of the rf mosfet results in a junction capacitance from draintosource (c ds ). these capacitances are characterized as input (c iss ), output (c oss ) and reverse transfer (c rss ) capacitances on data sheets. the relationships between the interterminal capacitances and those given on data sheets are shown below. the c iss 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 c ds source gate c gd c gs c iss = c gd + c gs c oss = c gd + c ds c rss = c gd drain characteristics one critical figure of merit for a fet is its static resistance in the fullon condition. this onresistance, r ds(on) , occurs in the linear region of the output characteristic and is specified at a specific gatesource voltage and drain current. the drainsource voltage under these conditions is termed v ds(on) . for mosfets, v ds(on) has a positive temperature coefficient at high temperatures because it contributes to the power dissipation within the device. bv dss values for this device are higher than normally required for typical applications. measurement of bv dss 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 10 9 w e resulting in a leakage current of a few nanoamperes. gate control is achieved by applying a positive voltage to the gate greater than the gatetosource threshold voltage, v gs(th) . gate voltage rating e never exceed the gate voltage rating. exceeding the rated v gs can result in permanent damage to the oxide layer in the gate region. gate termination e the gates of these devices are essentially capacitors. circuits that leave the gate opencir- cuited or floating should be avoided. these conditions can result in turnon of the devices due to voltage buildup on the input capacitor due to leakage currents or pickup. gate protection e these devices do 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 dampen 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. 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 fets operate optimally with a quiescent drain current (i dq ), whose value is application dependent. the MRF1508 was characterized at i dq = 150 ma, which is the suggested value of bias current for typical applications. for special applications such as linear amplification, i dq 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.
lifetime buy last order 30jun02 last ship 30dec0 2 MRF1508 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, athermal management and mounting method for the pld1.5 rf power surface mount package,o and engineering bulletin eb209/d, amounting method for rf power leadless surface mount transistoro 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, aimpedance matching networks applied to rf power transistors.o largesignal 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. twoport stability analysis with the MRF1508 sparameters provides a useful tool for selection of loading or feedback circuitry to assure stable operation. see motorola application note an215a, arf smallsignal design using twoport parameterso for a discussion of two port network theory and stability.
15 MRF1508 motorola rf device data package dimensions case 46602 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 millimeters inches a 0.255 0.265 6.48 6.73 b 0.225 0.235 5.72 5.97 c 0.065 0.072 1.65 1.83 d 0.130 0.150 3.30 3.81 e 0.021 0.026 0.53 0.66 f 0.026 0.044 0.66 1.12 g 0.050 0.070 1.27 1.78 h 0.045 0.063 1.14 1.60 k 0.273 0.285 6.93 7.24 l 0.245 0.255 6.22 6.48 n 0.230 0.240 5.84 6.10 p 0.000 0.008 0.00 0.20 q 0.055 0.063 1.40 1.60 r 0.200 0.210 5.08 5.33 s 0.006 0.012 0.15 0.31 u 0.006 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 3 4 1 af r l n k d b q e p c g h zone x zone w 0.89 (0.035) x 45 5    10 draft zone v s u resin bleed/flash allowable j 0.160 0.180 4.06 4.57 j
MRF1508 16 motorola rf device data motorola reserves the right to make changes without further notice to any products herein. motorola makes no warranty, represe ntation or guarantee regarding the suitability of its products for any particular purpose, nor does motorola assume any liability arising out of the applicati on or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. atypicalo para meters 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 ope rating parameters, including atypicalso must be validated for each customer application by customer's technical experts. motorola does not convey any license under it s patent rights nor the rights of others. motorola products are not designed, intended, or authorized for use as components in systems intended for surgical imp lant 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 cou ld 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 expens es, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized u se, even if such claim alleges that motorola was negligent regarding the design or manufacture of the part. motorola and are registered trademarks of motoro la, inc. motorola, inc. is an equal opportunity/affirmative action employer. mfax is a trademark of motorola, inc. how to reach us: usa / europe / locations not listed : motorola literature distribution; japan : nippon motorola ltd.: spd, strategic planning office, 141, p.o. box 5405, denver, colorado 80217. 13036752140 or 18004412447 4321 nishigotanda, shagawaku, tokyo, japan. 035487 8488 customer focus center: 18005216274 mfax ? : rmfax0@email.sps.mot.com touchtone 1 6022446609 asia / pacific : motorola semiconductors h.k. ltd.; 8b tai ping industrial park, motorola fax back system us & canada only 18007741848 51 ting kok road, tai po, n.t., hong kong. 85226629298 http://sps.motorola.com/mfax/ home page : http://motorola.com/sps/ ? MRF1508/d


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