JFet/pnp/npn

[vendettav]

ok this is not a question on which is what but rather how can you figure those out? i mean i'ev got these trannies about 10 or something. they've got a green dot on the top.. it's the modern package i forgot the name of but whatever. can i find it out with a multimeter or something??

[anchovie]

Don't they have a part number on them that you can Google for?

[Pigyboy]

You need one of these
http://www.peakelec.co.uk/acatalog/jz_dca55.html

[vendettav]

it aint got anything but the dots. green on the top.. blue on the flat side

[R.G.]

Old, old problem, with an old old solution.

To do this by hand, you do what the semiconductor tester/identification devices do. You use a diode-direction tester - the low 0hms scale of a multimeter will do - then you test each pin for diode conduction to the others. You note which pins conduct to which others, and the number of diode drops. Then you match that against your memorized table of what diode conduction is what for NPN, PNP, N-JFET, P-JFET, MOSFET, etc.

As a starter, the gate of a MOSFET conducts one way but not both to both D and S, the D and S conduct below 1K but not as well as a diode to each other.
The base of a bipolar conducts one way to both C and E, not the other way, and C and E don't conduct to each other. Which way they conduct tells you the polarity.

The semiconductor testers have just mechanized this bit of heuristics.

[vendettav]

Thanx R.G. as always!!! that makes a PERFECT sense

[R.G.]

Well, it would have been if it was not in error! 


This:

the gate of a MOSFET conducts one way but not both to both D and S,

is flatly wrong. The gate of a MOSFET doesn't conduct either way until it's destroyed. The gate of  JFET conducts to the channel one way but not the other.

Doh!

[vendettav]

thanx anyways, it was quite helpful, it was NPN i believe. i then tested their hFE and they varied quite a lot, 2 were around 460  500 and 2 or 3 around 640.. and one was 856 Ima try a booster with it! It's gonna yield some boost i guess!

lets see how it goes