# How to determine the emitter and collector of a transistor?

1. ## How to determine the emitter and collector of a transistor?

By using a multimeter to determine the Base, Emitter and Collector of a transistor... What i get is 0.6V and 0.57V... The positive of probe is base, but how to determine the Emitter and Collector.

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2. ## BJT transistor

by using multimeter, you will find that there is infinite resistance(open circuit) between E & C and drop across C will be more.

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3. ## Re: BJT transistor

wisepie,
The emitter to base reverse breakdown voltage is typically around 7V. You can insert a large resistor in series withe base, and measure the voltage at which the current starts to flow (avalanche current). The series resistance will prevent excessive current flow and consequent damage to the device. The terminal (E or C) that has the lowest breakdown voltage is the emitter.
Regards,
Kral

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4. ## Re: BJT transistor

I just want to know 0.57V is terminal (E) or terminal (C)

5. ## Re: BJT transistor

The junction with the lowest forward reading is the b-c junction. 0.57V in your case will be the b-c reading

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6. ## Re: BJT transistor

wisepie,
Your original post doesn't make it clear under what conditions the 0.57 and 0.6V readings are measured. I'm assuming that you are somehow forcing a known current through each junction (B-E, B-C), one at a time, and measuring the diode drops. You have two phenomena that tend to counteract. On one hand, the B-C junction hase a larger area, which would tend to lower the voltage for a given current. On the other hand, the Collector region has a lower doping level than the emitter region, which would ted to increase the B-C voltage for a given current. I'm interested in knowing how E-design came to his/her conclusion.
Regards,
Kral

7. ## Re: BJT transistor

I have been using this method for many years with my Fluke meter's diode testing function. The lowest reading is always the b-c junction, even if the reading differs by only 1 digit.

8. ## BJT transistor

The emitter will be the one with greater voltage drop and the other will obviously be collector.

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