N-channel MOSFETs

Haiben supplies N-channel MOSFETs from our Weforsemi line alongside the BJT, digital transistor and composite device families that surround them on real boards. For purchasing staff and hardware engineers, this page explains why the n channel mosfet is so often the default low-side switch, what our stocked surface-mount range covers, and how to read on-resistance against the gate voltage you will actually apply.

Why N-channel is the default switch

The n channel mosfet conducts with electrons rather than holes, and electron mobility in silicon is higher than hole mobility. For a given die area and voltage class, that generally gives a lower channel resistance than an equivalent P-channel device. This is established device physics rather than a claim about any specific part.

The practical consequence is simple. When a load sits between the positive rail and the transistor, the N-channel device is source-referenced to ground, so the gate drive is referenced to ground as well. Driving the gate is then straightforward. P-channel parts suit high-side switching, but they often need more die area for the same RDS(ON), and their gate has to be pulled below the source rail. Many designs therefore use the n channel mosfet for the main switching path and reserve P-channel MOSFETs for load-side control and reverse-polarity protection.

The Weforsemi range also includes bipolar and pre-biased parts, so around a switching stage you will usually find small-signal transistors handling level shifting, enable logic and signal routing while the MOSFET does the current-carrying work.

The stocked N-channel range

Our Weforsemi n channel mosfet listings are concentrated in the small surface-mount packages that suit compact control and load-switch circuits. The table below lists what the models and the manufacturers' published data state.

• VC9320A-1 — SOT-723, VDS 20 V, ID 1.0 A, RDS(ON) 160 mOhm typ at VGS 4.5 V and 180 mOhm typ at 2.5 V, ESD capability 3 kV HBM.
• VCAA3134KLC — SOT-883, VDS 20 V, ID 0.9 A, RDS(ON) below 250 mOhm at VGS 4.5 V and below 350 mOhm at 2.5 V; a high-density trench cell design for low on-resistance, optimised for switching performance.
• VC1012F — SOT-523, 150 mW, ESD 2000 V.
• VC7002HX — SOT-23, N-channel enhancement mode, VDSS 60 V, 350 mW, low RDS(ON), low gate threshold voltage, low input capacitance, ESD protected to 2 kV.

For higher-current or board-level power paths, see the power MOSFETs page. The complementary families are listed on our MOSFETs hub.

RDS(ON) at your actual gate voltage

On-resistance is quoted at a stated gate-source voltage, and the value changes with it. The VC9320A-1 is specified at both 4.5 V and 2.5 V, and the difference is visible: 160 mOhm typ versus 180 mOhm typ. The VCAA3134KLC likewise gives below 250 mOhm at 4.5 V and below 350 mOhm at 2.5 V.

The selection rule is to compare RDS(ON) at the gate voltage your circuit can guarantee, not at the highest figure in the datasheet. A 3.3 V logic rail driving a device characterised at 4.5 V will not deliver the quoted resistance, and the part will run warmer than the figure suggests. Check three points:

• The minimum gate drive your driver or logic output can hold over temperature and tolerance.
• Whether the part is characterised at that voltage, as the two parts above are at 2.5 V.
• Gate threshold voltage: VC7002HX is described as having a low gate threshold voltage, which matters for low-voltage drive.

Conduction loss follows I²R, so the RDS(ON) figure you select should be the one at your real gate voltage.

Load switching and power-path uses

A small n channel mosfet in SOT-723 or SOT-883 is a practical switch for LEDs, small fans, solenoids, relay coils and load-disconnect paths on a board. The VC7002HX's 60 V VDSS and low input capacitance suit switching nodes where a higher rail or faster edge is needed; the VC9320A-1 and VCAA3134KLC suit 20 V-class low-side switching.

Gate drive is often handled by a small-signal or pre-biased transistor. The VC143ZEF and VC143ZME NPN digital transistors integrate the base resistor network in the package, which simplifies the drive interface and reduces external parts.

Where a single package must combine functions, the composite family covers more than a plain MOSFET. VCMNT32D is a PNP power transistor with N-MOSFET in DFNWB2x2-6L, with ultra-low collector-emitter saturation voltage and high DC current gain. VC5853DCJ is a MOSFET-Schottky composite in DFNWB3x2-8L with Vrrm 20 V. These are worth examining when a design needs both a switch and its associated diode or gain stage.

Frequently asked questions

What package options do the stocked N-channel MOSFETs use?

The Weforsemi N-channel listings on this page use SOT-723, SOT-883, SOT-523 and SOT-23. These are surface-mount packages suited to compact control and load-switch circuits.

Why does the RDS(ON) figure differ between 4.5 V and 2.5 V gate drive?

RDS(ON) depends on the gate-source voltage applied. The VC9320A-1 is specified at 160 mOhm typ at 4.5 V and 180 mOhm typ at 2.5 V, so you should select against the gate voltage your circuit can actually maintain.

Do your MOSFETs include ESD protection?

Some do, as stated in the published data. The VC9320A-1 has ESD capability of 3 kV HBM, the VC1012F is rated at 2000 V, and the VC7002HX is ESD protected up to 2 kV. Check the datasheet for each part.