AO3400 34DG N Channel Mosfet Sot-23

Yes, this is the right small switch for a low-voltage board that needs a tiny SOT-23 N-channel MOSFET. It handles up to 30V and up to 5.8A at room temperature, and it turns on with a low gate voltage. If your old part is a 30V SOT-23 N-channel part with the same three pins, this one is a good match. Check the pins and the gate voltage on your board before you order. This is an original, high-quality part.

What it does

A MOSFET is a small electronic switch. A small voltage on its gate pin turns it on. When it is on, current can flow from the drain pin to the source pin. When the gate voltage is off, the switch is off. This part is an N-channel MOSFET, so it switches on the low side of a circuit.

It has three pins in a small SOT-23 case:

• Pin 1: Gate (G) — the control pin
• Pin 2: Source (S)
• Pin 3: Drain (D) — the pin that connects to the load

This part suits load switch jobs and PWM jobs. A load switch turns a small load on and off. A PWM job switches a load on and off very fast to control it. Its low on-resistance means it wastes less power as heat when it is on.

Who it fits

This part fits you if you repair small boards and you need a small 30V N-channel switch. It fits load switch work, PWM work, and small DC power switching work. It is a surface-mount part, so it fits boards made for SOT-23 parts. It does not fit boards made for big TO-220 parts. If your board has a big MOSFET with a metal tab and a screw hole, this small part is not the right fit.

Checks before ordering

Check these five things on your old part or your board before you order:

• N-channel, not P-channel. A P-channel part will not work in place of this one.
• Voltage. Your circuit voltage must stay at or below 30V. Do not use this part above 30V.
• Current. Your load current must stay within the datasheet limits. The 5.8A figure is at 25°C, and it drops to 4.9A at 70°C.
• Package and pins. Your board must have SOT-23 pads, and the pin order must match: Gate, Source, Drain. Compare with your old part before you solder.
• Gate voltage. The lowest on-resistance figure, 28 mΩ, needs a 10V gate drive. At 4.5V the max is 33 mΩ, and at 2.5V it is 52 mΩ. If your board gives a low gate voltage, the part will still switch, but its resistance will be higher than the 10V figure.

Never let the gate go above ±12V. That is the max gate voltage in the datasheet, and going past it can damage the part.

Specifications from the datasheet

All figures below are from the AO3400 datasheet, Rev 8, Dec 2011.

Spec	Value
Type	N-channel MOSFET, SOT-23
Drain-source voltage (VDS)	30 V max
Gate-source voltage (VGS)	±12 V max
Continuous drain current (ID)	5.8 A at 25°C; 4.9 A at 70°C
Pulsed drain current (IDM)	30 A max
Power dissipation (PD)	1.4 W at 25°C; 0.9 W at 70°C
On-resistance (RDS(ON))	28 mΩ max at VGS = 10V, ID = 5.8A
On-resistance (RDS(ON))	33 mΩ max at VGS = 4.5V, ID = 5A
On-resistance (RDS(ON))	52 mΩ max at VGS = 2.5V, ID = 4A
Gate threshold voltage (VGS(th))	0.65 V min, 1.05 V typ, 1.45 V max
Input capacitance (Ciss)	630 pF
Total gate charge (Qg)	6 nC typ, 7 nC max
Junction temperature (TJ)	−55°C to 150°C

You can view and download the datasheet for this part from the Datasheet button on this page.

If this part is not available, use one of these instead

If this exact part is not available, do not guess. A swap must match the old part on voltage, current, package, pin order, and N-channel polarity. A part with the same package but a different pin order will not work, even if the voltage and current look right.

Substitutes you can buy at SunTech Mall

Do not buy a big TO-220 MOSFET as a direct swap. It will not fit SOT-23 pads. The N-channel MOSFETs below are sold at SunTech Mall and do the same kind of switching job, but in a bigger package. Use one only if you can change the board layout to fit it, and only after you check its own voltage, current, and gate needs. Higher ratings do not make a part a drop-in swap — the small SOT-23 footprint is the blocker.

• IRF3710 100V 57A N-channel MOSFET, TO-220 — far more voltage and current headroom than this part (100V vs 30V, 57A vs 5.8A), on-resistance 23 mΩ max or less, gate limit ±20V (this part: ±12V), power limit 200W (this part: 1.4W). Bigger package, not a direct swap.
• IRF3205 55V 110A N-channel MOSFET, TO-220 — 55V and 110A, on-resistance 8 mΩ max or less, which is lower than this part’s 28 mΩ, so it wastes less heat at the same current. Still a big TO-220 part that will not fit SOT-23 pads. Not a direct swap.
• IRFB4115 150V 104A N-channel MOSFET — 150V and 104A, on-resistance 11 mΩ max or less. Same story: far more headroom and lower resistance, but a big TO-220 body that will not fit SOT-23 pads. Not a direct swap.

Warning: check the live page of any part above before you order. This text does not state its stock state. If you need the same small SOT-23 size, wait for this AO3400 part instead of forcing a big part onto a small board.

Other names for the same part (good to know)

People search for this part in a few ways. 34DG is the code in this listing title, and it is a word customers type when they search for this part. A09T is the small marking shown on the part body. AO 3400, with a space, is the same part number written with a space. Note: 34DG was not found as a body marking in the AO3400 datasheet, so this page does not claim it as a datasheet marking. It is kept here because customers use it to find this listing.

Frequently Asked Questions

What does 34DG mean on this part?

34DG is the code in this listing title. Customers type 34DG when they search for this AO3400 part. The body marking shown in part guides is A09T.

What are the pins of the AO3400?

Pin 1 is Gate, Pin 2 is Source, and Pin 3 is Drain. Always compare with your old part before you solder, because a wrong pin order will stop the board from working.

Can I use the AO3400 on a 12V board?

Yes, on voltage alone. 12V is below the 30V max. You still need to check the load current and the gate voltage your board gives.

Can I swap this N-channel part with a P-channel part?

No. A P-channel part works the other way round. It will not work in place of this N-channel part.

What is the live price of this part?

Check the live price on the website. No fixed figure is given here, so the page always shows the current one.