1N4148 A2 SMD HIGH SPEED SWITCHING DIODE SOD-123

Looking for an A2 diode? If the tiny diode on your board is marked A2, this is the part you are looking for. It is the small SMD version of the well-known 1N4148 switching diode, in a SOD-123 body. It switches fast, it takes up very little space, and it is made for small signal work on crowded boards. This is an original, high-quality part.

What this diode does

A diode lets current flow in one way and blocks it in the other way. This diode does that job at high speed. It is used for fast signal switching, for shaping a waveform, for clamping a voltage, and for routing a small signal to the right place. Its reverse recovery time is only 4.0 ns at most, so it can switch on and off very fast without smearing the signal.

It is a small signal diode, not a power diode. It is made for low current signal circuits, such as control boards, logic circuits, and the small signal sections of power supplies and solar inverter boards. It is not made to carry large power currents.

Who this diode fits

This diode fits you if you are repairing a board and the old part is a small SMD diode marked A2 or T4 in a SOD-123 body. It also fits small new builds where you need a fast, small, surface-mount switching diode and your board has SOD-123 pads.

It fits repair work on solar inverter control boards, power supply boards, and other small signal boards, as long as the circuit needs a 1N4148-type switching diode and the voltage and current stay within the limits in the table below.

Checks before you order

Read the marking on the old part first. A2 means this SMD 1N4148. Two codes are printed on this part type: A2 and T4. Both point to the same SOD-123 1N4148W diode. Do not treat a code on its own as full proof — check the body size too.

Check the body size too. This page is for the SOD-123 body. If your old part is smaller, such as a SOD-323 body, this part will not fit its pads, even if the code looks close. Measure the old part or match it against the SOD-123 pads on your board before you order.

Check the band on the part. The band marks the cathode end. Put the new diode in the same way round as the old one. A diode put in backwards will block the signal instead of passing it.

Check the circuit limits. The peak reverse voltage must stay at or below 100 V, and the forward current must stay within the limits in the table below. If your circuit needs more current or a higher voltage, this diode is the wrong pick, and you need a different part.

This diode is a surface-mount part. It solders onto pads on the board surface. It does not have wire leads, and it does not fit through-hole pads without rework.

Specifications

All figures below are for the SOD-123 1N4148W diode, at +25 °C unless noted.

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

If this SOD-123 part is not on hand, do not pick a random diode with a close name. Use a part with the same job and the same limits, and check the fit first.

Substitutes you can buy at SunTech Mall

Practical substitute: 1N4148 Small Signal Diodes (DO-35) — this is the same 1N4148 diode job in a through-hole glass body with wire leads. It is practical, not drop-in. Before you use it, check three things: the package and pinout (leads, not SMD pads), the soldering method (through-hole work, not surface-mount pads), and the board space (the DO-35 body and leads need holes and room). If your board has SMD pads only and you cannot rework it, this substitute will not fit. Check the live SunTech page for its current state before you order.

Warning: a part that only shares a marking code is not a safe pick on its own. Codes differ by maker, and the same code can point to a different body size. Match the part number, the body size, and the pads, not just the code.

Other names for the same part (good to know)

This part is also known by names that buyers type when they search. 1N4148W is the SMD part number for this SOD-123 diode. A2 diode is the name buyers use when they read A2 printed on the tiny body. T4 diode is the name buyers use when they read T4 printed on the same type of body. 1N4148 SMD and SOD-123 switching diode are the plain names for the same part. If you see A2 or T4 on a SOD-123 body, and the circuit needs a 1N4148 switching diode, this page is the right match.

Frequently Asked Questions

What does A2 mean on this diode?

A2 is a short code printed on the body because the full part number does not fit on such a tiny part. A2 means 1N4148W in a SOD-123 body. So if your old diode says A2 and it sits on SOD-123 pads, this is the part you need.

What is the difference between A2 and T4?

There is no difference in the job. A2 and T4 are two codes for the same SOD-123 1N4148W diode. Check the body size as well as the code.

Is the DO-35 1N4148 the same as this SMD part?

It does the same diode job, but it is not the same fit. The DO-35 part has wire leads and fits through holes in the board. This page is the SMD part with pads for surface mounting. Use the DO-35 part only if you can do through-hole work and your board has room for it.

Which way round does this diode go?

The band on the body marks the cathode end. Fit the new diode with its band in the same place as the old diode’s band. If it goes in backwards, it will block the signal it should pass.

Can I use this diode for high current power work?

No. This is a small signal diode. Its forward continuous current limit is 300 mA, and its power dissipation limit is 400 mW. For high current power work you need a power diode or rectifier with higher limits, not this part.

What is the price of this diode?

Check the live price on the website. No price figure is given here, so the live page is the only place to see the current price.

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