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# determine transistor 's pins

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#### smiles

Suppose that I have an Ohmmeter, and I am guided the way to determine which pin of transistor is 'Base' pin ( Ohm value between 'B' and 'C' approximately the same to 'B' and 'E').
Could you help me the way to determine the two rest pins, which is 'Collector', which is 'Emitter' ?
Thanks !!!

generally some multimeters have option of checking diodes and in that the resistance value of diode is displayed (i.e.very high value)... if that option is available then you can check using the fact that the emitter base junction would be less resistive than the collector base junction....

Hi, you are asking a good old days question well, you can refer to any "analogue" multimeter manuals (eg sanwa 360, 361 ... ) and the answer will be there. Bye.

A very easy way to act:
1) suppose you know if the transistor is a PNP or NPN ( here following is the idea for the NPN transistor )
2) Suppose you know which pin is the base.
3) Suppose you know where is the positive ( higher voltage ) of the two pin of the ohmeter ( in the digital ones is normally the red wire, but take care that in the old analog multimeters ( ICE as example ) the black wire si at higher voltage; suppose you are using a digital multimeter.
4) Let's name pins 1, 2 and 3, considering base pin n° 2

If you have 4 yes let's continue.

a) Connect the red terminal to pin 1 and the black terminal to pin 3
b) connect pin 2 of the transistor to pin 1 and read and record the voltage
c) Connect the red terminal to pin 3 and the black terminal to pin 1
d) Connect pin 2 to terminal 3 and read and record the voltage
e) check the lower voltage between step b) and d); the lower detected ( suppose is b)) means that the collector is terminal 1, if the lower is d) means the collector is terminal 3.

A short explanation.
When you connect togheter collector and base the saturation voltage of the CE junction is always lower than the voltage of the junction BE or BC.

Mandi

you can also try using the setting available in the multimeter for finding the hfe of the transistor... plug in the three pins in both ways possible and the one with higher hfe means that it has been correctly plugged in and you can find the terminals from that....

Hi ! Thanks for your replies ! My multimeter can measure ACV, DCV, DCA, Ohm, dB , hfe
A.Anand Srinivasan said:
you can also try using the setting available in the multimeter for finding the hfe of the transistor... plug in the three pins in both ways possible and the one with higher hfe means that it has been correctly plugged in and you can find the terminals from that....
Thanks !!!

hi,smiles
Try to imagine that if the type of it is NPN.it can be show like picture below.

use VOM(choose ohmmeter mode and choose (Rx1 scale).not using DVM.This way is only right in case U use VOM to test.
Fisrt
place randomly 2 prop of VOM on 2pin of 3 pin of transistor.then you change position of two prop(ex: first red pro is position 1 , black prop is position 2 then red pro is position 2 , black prop is position 1).After 2 times change position on of Prop, If R mesured result is infinity or nearby it then TWO pin of that couple is CE. and We determine the other pin is Base.
Then we determine where is C and where is E
Place black prop on BASE, and red prop on other pin(C or E).If bolth cases( prop plce on E , and prop place on C) the mesured result is infinity or nearby it
that transistor type PNP.Else If it type NPN.
the third
IF type is NPN(place black prop on BASE) or type is PNP(place red prop on BASE).and place other Prop on one other pin.If the result mesured is not infinity or nearby infinity that pin prop place on is E , and the other pin is C.
cheer,
note that between B and E is one Zener diode , and between B and C is normal diode.

### smiles

Points: 2
there would be three slots for the three pins of transistor in each multimeter
just like the blue slotted place in the above multimeter.... since you know the base jus place the base in its slot and try the two other terminals in the two possible configurations and the configuration which gives the highest hfe is the right one in terms of slots usage... this is due to the doping concentration of the emitter and collector.....

Hi,A.Anand Srinivasan
Some transistor are made in china,their orther Pins is BCE , some is CBE

smiles said:
Hi ! Thanks for your replies ! My multimeter can measure ACV, DCV, DCA, Ohm, dB , hfe
A.Anand Srinivasan said:
you can also try using the setting available in the multimeter for finding the hfe of the transistor... plug in the three pins in both ways possible and the one with higher hfe means that it has been correctly plugged in and you can find the terminals from that....
Thanks !!!

Anand is right.
Smiles, in your case with your DVM, you need to determine the B pin of the transistor using the "Diode test" range and then "hfe ratio" with swapping the rest 2 pins for distinguishing the C and E.

For the reason why, you should refer to any book of transistor theory. When you know well about the transistor and practise much, you will find out by yourself more tricks in testing transistors, it is very easy and funny.

nguyennam

hbaocr said:
Hi,A.Anand Srinivasan
Some transistor are made in china,their orther Pins is BCE , some is CBE

I've come across those transistors too.... actually the hfe part of the multimeter would have four slots taking the BCE configuration also into account....

smiles said that supposing that he could find the base terminal using resistance value then could we help him find the other two terminals so only i replied like that....

Points: 2