Is there any way to find more info about a tranzistor?

I need to replace one on a circuit board, which controlls interior car lighting fade-in/out (12V).The lettering in it is extremely small but I can make out NP100. When I look at catalogs, I should also know the wattage, but I have no way to find out. Thanks!?

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ro0ter4 years ago
More like a fet? Mosfet?


Is it smd? Tht? The wattage doesn't really matter, in fact you should select the wattage according to the load, still pick a larger one. That's the reason that made it fail: high load. OR maybe its pwm controller toasted its input... check the resistor between the ic and the mosfet, you should get a hold of what's the problem.

ro0ter ro0ter4 years ago
earlier I ment to first check the mosfet gate driver (not the resistor; i was a bit in the "transostor" mood), maybe it`s not the mosfet itself. also check the ic for output, maybe it got toasted. who knows. it`s hard to tell what went wrong without being able to test it on the spot.

PS: you could visit a jewler and have him read the whole code ;)
Fyod (author)  ro0ter4 years ago
THT. It's this bit. Seems somone tampered with the "legs". It could probably be soldered, but I'd rather just buy a new part.
Btw,: if it only says 'NP100", does that mean its PNP or NPN?
ro0ter Fyod4 years ago
Hi Fyod,

Please note that FET`s are P-channel or N-channel (instead of PNP / NPN)

If you are asking about the datasheet I sent you, that`s a P-ch MOSFET. Your (incomplete) code seems also to denote a P-ch MOSFET (gate connects to the driver circuit, drain connects to + and source goes all way to your lights which are further connected to - aka your car`s chasis).

It`s kindda impossible to use N-ch MOSFETs in automotive electronics since you would have to connect it between the devices it powers and ground (car chasis). It would be awkward to have two wires for each device it powers instead of 1.

So go with the P-ch MOSFET, 99,9% positive.
Fyod (author)  ro0ter4 years ago
I found a picture of a very similar module, hope it helps. It's almost exactly the same, but mine has the TO-92. The middle connector goes to one of the resistors, left to another resistor, right to a third resistor. The module has 5 leads and is a replacement for the interior lighting relay.
Fyod (author)  Fyod4 years ago
FETs are usually used as ground side switches as in the cct below.

[ sorry for deleting-adding comments, i know it`s the 3rd time, maybe an edit button won`t harm anyone ;) ]

Indeed, but not in automotive industry.

Any device (light, starter motor, relay) may be (actually is) controlled by a fet (or relay). We all know that these devices are grounded to the car chassis.

The device load is always connected to fet source so that the device resistance/inductance/capacitance/etc won't affect the function of the fet (you open the fet by applying voltage between gate and drain, the load wire goes between source and drain).

Now, in order to use the circuit in the figure above, to avoid connecting the device to the fet's drain, the automobile manufacturers would have to add one wire from the battery to the device (positive 12/24 v) and one EXTRA wire from the device to the fet (negative aka ground). Correct me if i am wrong, but an automobile ALWAYS has its devices connected directly to the ground (car chassis, if not from carbon/glass fiber) and there is only a SINGLE wire coming from the control block.

I won't say more on this, most of you already know what i'm talking about.

Fyod, hope you can fix it. Although i work with such things, i don't know them all by heart.

Regards to all of you!

PS: I'm not britanica encyclopedia, discovery channel nor wikipedia website. I'm only a humble software/hardware engineer in industrial automation and automotive electronics.
Are you sure its transistor ??
TO ADMIN: when I click the "reply" button, please add $("#PostCommentFormBODY_editor").focus()... you`ll make our lives better ;) thanks

now steveastrouk: if the function of the component is how fyod describes it, then it`s definitely a transistor. and if it controls light dimming, then it`s definitely a mosfet (dissipates almost no heat when turned on, and acts much more like a schmidt trigger; requries voltage to be turned on, not current).
I wouldn't bet on it. There are single chip solutions for courtesy lights which come in TO92 cans. Allegro used to do them.

You should never assume you have all the information from questions here !
Fyod (author)  steveastrouk4 years ago
I'm pretty much just judging by the shape, found out it should be a bipolar transistor.
You can get ALL sorts of things in a TO92 package - radio receivers, regulators, temperature sensors, mosfets.....and transistors.

Post some pictures ?
Fyod (author)  steveastrouk4 years ago
Sorry, don't have it here with me. It's a pretty simple circuit with one mosfet, a couple caps, a TLC272 amp, and some 6 or 8 resistors.
No need for recievers, regs, temp.