Distinguish FET from BJT from ? with DMM

[baldguyfromblackpool]

A follow on from my earlier thread about copying a relay controller.

I have one final 3-legged SMT component left that I don't fully understand. It's in a circuit position that makes it reasonably clear which should be the gate, source and drain (or base, emitter and collector)

Measured resistance between pairs of legs using both normal 2k resistance range, and the diode test mode. I was expecting to be able to clearly identify either the insulated gate of a FET, or the diode characteristics of a base-emitter junction, and thereby decide whether it was a FET or a BJT.

Unfortunately my results seem to identify it as a "?"

It's clearly meant to switch on and off a relay coil based on an applied 3V DC control signal, if it's not a transistor of some sort what could it be?

 

[bertus]

Hello,

You can not measure the part incircuit.
There will be surrounding parts that will influence the measurement.
Here is a list of possible parts for smd code n3:

Marking of electronic components, SMD Codes N3, N3***, N3030LS, N306AD. Datasheets BC817DS, BFG520W, BZX384-B43, DMN3030LSS, ISL9N306AD3, ISL9N306AD3ST, MMSZ5263, Si2303CDS.

Marking of electronic components, SMD Codes N3, N3***, N3030LS, N306AD. Datasheets BC817DS, BFG520W, BZX384-B43, DMN3030LSS, ISL9N306AD3, ISL9N306AD3ST, MMSZ5263, Si2303CDS.

www.s-manuals.com

The size of the part may narrow the search:


Bertus

 

[baldguyfromblackpool]

My cheap plastic calipers measure 2.8mm, so I think SOT-23

By removing one 10k resistor from the board I figured I then had the part isolated and fully out-of-circuit, albeit with a couple of components still 'hanging off' each leg - a relay coil with parallel diode on the source followed by a white wire, a 1k resistor on the gate and a red wire, and a piece of black wire on the drain. But, none of these 3 seperate 'strings' of components in continuity with one another (except I did leave the capacitor c3 in)

I did notice there are a few 3-leg N3* devices in SOT-23 described as 'voltage detector' e.g. https://shorturl.at/qDGB6

So I'm wondering if this is not a discrete transistor as such, rather, some kind of dedicated black box IC.



Wasn't quite sure about the last M so took another pic, pretty sure it's M

 

[bertus]

Hello,

Here is a larger list for n3;

The SMD components marking codes database - Starting with 'N3'

Bertus

 

[baldguyfromblackpool]

Thanks - there were 5 in particular I had a close look at the datasheet, in that list. Couldn't find a 100% perfect match but I'm pretty sure now, what I've got is something very similar.

I thought they were going to stop at toasters and lightbulbs, but now even discrete transistors have computers built-in.