Test transistor base emitter collector how to#
Test transistor base emitter collector download#

You may also want to look up the 'wet finger test', but I've not gotten it to work well and it's clumsy for me on small transistors. In the transistors I've tested this way, the differences are small (one to a few parts in a thousand) and I found that the gain test is the fastest and most reliable. You can measure the junctions' voltage drops with a DMM's diode test or measure the resistances the emitter-base resistance or voltage drop should be a bit higher. Testing of PNP transistor The PNP transistor is attached to the device with corresponding pin terminals and switch on the circuit. The orientation with the highest gain tells you the collector and emitter leads. Then insert the transistor into the appropriate socket of the HF meter and note the gain reverse the collector and emitter leads and note the gain again. A continuity tester or ohmmeter can tell you whether the transistor is PNP or NPN and identify the base lead. Connect the leads of the meter to the emitter and the collector. If you don’t have one of those a digital meter with a diode test will work. The quickest method is probably to buy one of those $5 Harbor Freight meters that has a small-signal transistor test socket. You can use a transistor tester with 3 leads. The datasheet is the best way, but not usable when you have transistors with non-standard or in-house markings (I have a box of a number of such transistors). Kris and Steve have given some good advice. I haven't tried this method but it should work. If the transistor has a collector-emitter diode, the voltages will be quite close together but the result should still be valid. It won't work if the transistor is leaky, or is a germanium transistor (the same thing, really). It should work on transistors with base-emitter resistors (although not because of Zener breakdown). This test may not work on Darlington transistors you may need a higher voltage (e.g. The pin that gives you the HIGHER voltage reading is probably the EMITTER. Touch the positive probe of your multimeter to each of the other terminals in turn. Connect positive of your voltage source to the base of the transistor.ģ. Connect negative of your voltage source to the negative probe of the multimeter.Ģ. Touch the negative probe of your multimeter to each of the other terminals in turn.ġ. Connect negative of your voltage source to the base of the transistor.ģ. Connect positive of your voltage source to the positive probe of the multimeter.Ģ.

Test transistor base emitter collector how to#

You need a DC voltage of at least 12V (from a power supply or a battery) and a digital multimeter with a high-resistance (10 megohms) input set to measure voltage.Īssuming you have an NPN, here's how to test it.ġ. If we plot the collector current of the transistor against the collector-emitter voltage for different base currents, we will obtain graphs similar to the. If you can't find out that way, you can probably measure for Zener breakdown of the base-emitter junction.

Test transistor base emitter collector download#

Normally, you read the part number off the device, Google it, download the data sheet, and see which pin is what.