Component Comparison: MMBF5485 vs IMBF170R450M1XTMA1

Quick verdict

For low-voltage, low-current RF amplification and switching at frequencies up to 400 MHz, the MMBF5485 is the clear choice due to its JFET technology and low noise figure. For high-voltage power switching requiring handling of currents near 10 A and blocking voltages up to 1700 V, the IMBF170R450M1XTMA1 excels with its SiC MOSFET technology and rugged TO-263 package.

Spec comparison table

SpecMMBF5485IMBF170R450M1XTMA1Notes
ConfigurationN-Channel JFETN-Channel SiC MOSFETDifferent device types; JFET for RF, MOSFET for power switching.
Current rating (continuous)10 mA9.8 A (typ Tc)IMBF170R450M1XTMA1 supports ~1000× higher current, suitable for power applications.
Frequency400 MHzNot specified (power MOSFET, low MHz range)MMBF5485 specified for RF; IMBF170R450M1XTMA1 not designed for RF frequencies.
GainNot specifiedNot specifiedGain not relevant for power MOSFET; MMBF5485 gain implied by JFET RF use.
Mounting typeSurface Mount (SOT-23-3)Surface Mount (PG-TO263-7-13)MMBF5485 is a small SOT-23; IMBF170R450M1XTMA1 is a large power package (TO-263 style).
Noise figure4 dBNot specifiedMMBF5485’s 4 dB noise figure suitable for low-noise RF front ends; MOSFET noise figure not given.
Output power maxNot specifiedNot specifiedNo data; MMBF5485 limited by low current; IMBF170R450M1XTMA1 can handle high power dissipation.
Package caseTO-236-3, SC-59, SOT-23-3TO-263-8, D2PAK (7 leads + tab)Different footprints and thermal capabilities; IMBF170R450M1XTMA1 allows better heat sinking.
TechnologyJFETSiC FET (Silicon Carbide MOSFET)SiC allows high voltage and temperature operation; JFET optimized for RF.
Voltage rated (max drain-source)25 V1700 VIMBF170R450M1XTMA1 supports >68× higher blocking voltage.
Voltage test15 V15 VSimilar test voltage, but device ratings differ greatly.
Capacitance (typ)Not specified5 pF (typ)IMBF170R450M1XTMA1 input capacitance low for power MOSFET, but absolute value may be high for RF.
Continuous DC drain current max10 mA6.9 A (max)IMBF170R450M1XTMA1 supports orders of magnitude higher currents.
Continuous DC drain current typ10 mA9.8 A (typ)See above.
Drain-source on-state resistance typNot specified450 mΩ @ 12 V, 25°CIMBF170R450M1XTMA1 Rds(on) is moderate; no comparable data for JFET.
Gate charge total typNot specified4 nC (typ)Low gate charge for a high-voltage SiC MOSFET; no comparable data for JFET.
Gate charge total maxNot specified11 nC @ 12 VSee above.
Gate-source threshold voltage typNot specified4.5 V (typ)IMBF170R450M1XTMA1 requires higher gate voltage drive than typical logic MOSFETs.
Gate-source voltage max±20 V+20 V / -10 VBoth tolerate similar gate voltage ranges; IMBF170R450M1XTMA1 supports negative gate voltage.
Junction temperature maxNot specified175 °CIMBF170R450M1XTMA1 supports high TJ for power applications.
Power dissipation max (Tc)Not specified107 WIMBF170R450M1XTMA1 designed for high power dissipation; MMBF5485 is low-power device.
Switching speed (typ)Not specified50 nsIMBF170R450M1XTMA1 switching speed typical for power MOSFET; MMBF5485 specified for RF freq.
Package size (length)~2.9 mm (SOT-23)15 mm (TO-263)IMBF170R450M1XTMA1 is physically much larger, affecting PCB layout and thermal management.
Thermal resistance typNot specified62 K/WIMBF170R450M1XTMA1 package thermal resistance is moderate, requires heat sinking.
Noise figure4 dBNot specifiedMMBF5485 optimized for low noise figure in RF; IMBF170R450M1XTMA1 not intended for low noise.
Storage temperature minNot specified-55 °CBoth support typical industrial storage temperatures.

Design trade-offs

The MMBF5485 and IMBF170R450M1XTMA1 target fundamentally different application domains, reflected in their electrical and physical characteristics. The MMBF5485 is a low-voltage, low-current JFET optimized for RF front-end stages, operating up to 400 MHz with a 4 dB noise figure. Its 10 mA current rating and 25 V max voltage limit make it unsuitable for power conversion or high-current switching. Its small SOT-23 package facilitates dense PCB layouts in compact RF modules but offers minimal thermal dissipation.

In contrast, the IMBF170R450M1XTMA1 is a silicon carbide (SiC) MOSFET rated for 1700 V blocking voltage and nearly 10 A continuous current at 25°C case temperature. Its TO-263 package allows substantial heat sinking and a maximum power dissipation of 107 W (Tc). This device is designed for high-voltage power conversion, industrial inverters, or motor drives, where ruggedness and high efficiency at elevated voltages and currents are critical. The SiC technology provides benefits in switching speed and thermal stability compared to silicon MOSFETs, although gate drive voltages are relatively high (12–15 V recommended) and gate charge is moderate (~4 nC typical).

From a gate drive perspective, the MMBF5485 requires minimal drive considerations due to its low current and JFET nature, while the IMBF170R450M1XTMA1 demands a robust gate driver capable of delivering up to 11 nC total charge at voltages up to 15 V, with attention to gate voltage limits and transient swings. The higher gate charge and threshold voltage (~4.5 V) of the SiC MOSFET necessitate careful drive timing to minimize switching losses and avoid device stress.

Thermally, the MMBF5485 dissipates negligible power and requires no special heat sinking beyond standard PCB layout. The IMBF170R450M1XTMA1, capable of over 100 W dissipation, requires a dedicated heat sink or thermal pad and PCB copper area to maintain junction temperatures within limits. Layout must consider low inductance gate drive paths and sufficient copper for heat spreading.

Cost-wise, the IMBF170R450M1XTMA1 will be significantly more expensive due to its SiC technology, large package, and power ratings. The MMBF5485 is a low-cost, mass-produced RF transistor suitable for high-volume, cost-sensitive designs.

Use-case fit

Choose MMBF5485 when…

Choose IMBF170R450M1XTMA1 when…