MMBF5485 vs AO6604: Component Comparison for Power Electronics Engineers

Quick verdict

For low-current, high-frequency analog/RF switching or amplification applications, the MMBF5485 JFET offers superior performance due to its 400 MHz frequency capability and low noise figure. Conversely, the AO6604 MOSFET array excels in power switching and digital load driving scenarios, supporting up to 3.4 A with logic-level gate drive and integrated complementary N- and P-channel devices.

Spec comparison table

SpecMMBF5485AO6604Notes
ConfigurationN-Channel JFETN- and P-Channel MOSFET ArrayAO6604 offers complementary pairs, enabling push-pull stages; MMBF5485 is single JFET
Current rating (continuous)10 mA3.4 A (N-channel), 2.5 A (P-channel)AO6604 supports >300× higher continuous current; critical for power stages
Frequency400 MHzNot specified (low-frequency power device)MMBF5485 is suitable for RF up to 400 MHz; AO6604 is not designed for RF applications
GainNot specifiedNot specifiedJFETs generally provide intrinsic gain; MOSFETs do not
Noise figure4 dBNot specifiedMMBF5485’s 4 dB noise figure is relevant for low-noise RF front ends
Output power maxNot specified1.1 WAO6604 rated for 1.1 W power dissipation, supporting higher power use
Package caseTO-236-3 / SC-59 / SOT-23-3SC-74 / SOT-457 (6-pin TSOP)AO6604 package larger and different pin count; affects PCB footprint
Mounting typeSurface MountSurface MountBoth are SMT, suitable for automated assembly
TechnologyJFETMOSFET (Metal Oxide)Different semiconductor technology affects drive and switching characteristics
Voltage rated25 V20 VMMBF5485 has slightly higher voltage rating
Voltage test15 VNot specifiedMMBF5485 test voltage specified; AO6604 datasheet does not specify test voltage
Drain-source voltage maxNot specified20 VAO6604 maximum voltage rating given; MMBF5485 voltage rating above
Gate drive voltageNot specified (JFET)4.5 V logic level gate driveAO6604 designed for direct drive from logic-level signals
Gate charge (Qg)Not specified3.8 nC @ 4.5 VAO6604’s gate charge relevant for switching losses and gate driver sizing
Input capacitance (Ciss)Not specified320 pF @ 10 VAO6604 input capacitance affects switching speed and gate driver requirements
Threshold voltage (Vgs_th)Not specified1 V max @ 250 µAAO6604 threshold voltage suitable for logic-level drive
Operating temperature rangeNot specified-55°C to 150°C (TJ)AO6604 extended temperature range suitable for harsher environments

Design trade-offs

The MMBF5485 is a JFET optimized for low-level RF and analog signal roles, with a 400 MHz frequency rating and a 4 dB noise figure. This makes it suitable for front-end amplification or switching in RF circuits where low noise and high-frequency response are essential. However, its continuous current rating is only 10 mA, limiting its use to signal-level applications rather than power switching.

In contrast, the AO6604 is a complementary MOSFET array with much higher continuous current ratings (3.4 A N-channel, 2.5 A P-channel) and a maximum power dissipation of 1.1 W. The logic-level gate drive (4.5 V) and relatively low Rds(on) of 65 mΩ at 3.4 A make it well-suited for low-voltage DC power switching, digital load driving, and small motor control. Its gate charge of 3.8 nC is modest, but much higher than a JFET’s gate capacitance, which impacts switching speed and gate driver design.

Thermally, the AO6604 requires careful PCB layout with adequate copper area or a heat sink to dissipate up to 1.1 W continuously, especially near its maximum current rating. The MMBF5485, with significantly lower power dissipation due to its low current, has minimal thermal concerns in typical applications.

The MMBF5485’s SOT-23-3 package is more compact and common for RF signal transistors, whereas the AO6604’s 6-pin TSOP package is larger and designed to accommodate the dual MOSFET array. This affects PCB footprint and routing complexity, especially in dense designs.

From a firmware and gate drive perspective, the AO6604 requires a dedicated gate drive signal with logic-level voltage and appropriate timing to minimize switching losses and avoid shoot-through in complementary stages. The MMBF5485, being a JFET, does not require gate drive voltage swings and behaves more like a voltage-controlled resistor, simplifying drive circuitry but limiting power handling.

Cost-wise, JFETs like the MMBF5485 tend to be more expensive per unit than discrete MOSFETs, but the AO6604’s integrated complementary array could reduce BOM count and assembly cost in complementary switch designs.

Use-case fit

Choose MMBF5485 when…

Choose AO6604 when…

Drop-in compatibility

These parts are not pin-compatible or footprint-compatible. The MMBF5485 is a 3-pin device in a SOT-23 package (TO-236-3), whereas the AO6604 is a 6-pin complementary MOSFET array in a SC-74 (SOT-457) package. Direct substitution would require a PCB redesign, including layout changes and different gate drive circuitry.

Alternatives to consider