transistor

I do a range of nice cheap multimeters by mail order. <Splutter>

Common base and common emitter are ways of configuring transistors in amplifier circuits, Chief, or at least they were when I was a lot younger and not past it. <Wheeze, cough>

Come on, please do your homework by yourself. Open up your electronic study books and there is some explaining inside your study books telling you how to check the transistor.

Hi all,

Maybe not a homework question, but maybe an amature enthusiast or someone wanting to fix his TV to watch the Grand Prix? :)

Simply put think of a Transistor as two Diodes pointing at each other. To test a diode you need to measure the resistance between the legs both ways. i.e. once with the positive lead on the anode and the negative lead on the cathode (i.e. the two legs of the diode). You would then swop the leads around and again measure the resistance.

If the diode is ok, you would have measured infinite resistance in one direction and almost no resistance in the other direction.

So you have only two possibilities to measure for a diode with two legs. Now you apply this to the transistor and you will be able to measure whether it is ok.

To determine whether the transistor is is a common base, emmiter or collector - impossible on its own by just measuring. You need to look at the circuit to determine this.

Hang on....... This is now starting to smell like homework!

Regards,

Craig

I think it is a homework, anyway just follow these steps to test your transistor.

You got to see what type of transistor your are testing. It is an NPN type or PNP type. You have to check the transistor code and the data sheet.

Example for NPN type of transistor.

By using an analog multimeter.

To check the transistor "Base"

1) Select the range to x 2K ohm range and check your 0 ohm by shorting both test lead together. Make sure that the reading is at 0 ohm.

2) Put one of the test lead to one of the transistor leg and measure the other two transistor leg with the other test lead. You should get both transistor leg with the same ohm value. That will be the "base" of the transistor.

Sample;

Put the black test lead to the 1^st leg and test the 2^nd and 3^rd transistor leg with the "Red" test lead for the ohm values. If the Ohm values is same, between the transistor 2^nd leg and 3^rd leg, then, the 1^st transistor leg will be the "base" of the transistor. If not, then you had repeat the same test again with the 2^nd transistor legs and so on

To Check the Collector and the Emitter leg of the transistor

1) Select the range to x 200K ohm range and check your 0 ohm by shorting both test lead together. Make sure that the reading is at 0 ohm.

2) Since you have identify the "base" of the transistor leg, the other 2 transistor legs will be either the "Collector" and the "Emitter"

3) Put one of the "Red" test lead to one of the transistor leg and the other "Black" test lead to the other of the transistor legs. If you get some reading, the transistor leg with the "Black" test lead will be the collector and the transistor leg with the "Red" test lead will be the emitter. If no ohm reading available, repeat the other ways.

Well, that how we test and check the transistor legs.

Correct me if I am wrong.