What is a bipolar transistor and how to check the multimeter?

  • Dec 24, 2019

Anyone, not even owning the subtleties of Radio Engineering and Electronics, familiar with the term "bipolar transistor". But what is it and how the electronic component working - known far at all. Many fans are also interested in the issue if it is functional.

What it is

Bipolar transistor - is a classic semiconductor device, the principle of which is based on the two possibilities of its constituent p-n junctions. Moreover, the manufacture, they may be formed in two combinations, designated as n-p-n and p-n-p structure (pictured below).

By combining the two transitions possible to obtain a device capable of varying the parameters supplied to its input signal, increasing the amplitude in the hundreds of times. The average (total) of the transition structure is called the base and located on either side plots - the emitter and collector.

Note:The first received its designation because of the fact that it carried out the emission of electronic charge carriers, and the second - because in this area, will be picking up.

Due to the flow control capabilities of electronic media transistor and acquired its amazing properties amplify signals.

How to check the transistor

For understanding of the verification of the bipolar transistor, it is convenient to represent a pair of opposite or back diodes included (depending on the conductivity type). The structure of the p-n-p will appear as shown in the photo below:

The use of such graphic techniques is very convenient from a practical point of view. It allows you to verify the health of the transistor by measuring the resistance of the two diode junctions.

Important! From practice it is known that for manufacturing silicon junction resistance in the forward direction is an average of 0.6 volts (the same value for analogues of germanium is equal to 0.2-0.3 volts).

When measuring the resistance in the reverse direction should be displayed on the display infinity. It follows that, by measuring the transfer of two diodes, it is possible to conclude that the health of the transistor.

So, to test it is necessary to do the following:

  • Take a multimeter and put it in the diodes measurement mode.
  • Next you need to attach the ends of the probe to the base and collector in the forward direction (pictured above).
  • The device should show 0.6 volts.
  • This is followed by connecting the probe to change polarity, then the score is displayed a "1" (infinity).
  • Thereafter, the same operation is done with the second transition (results should be similar).
  • In conclusion, you need to touch the probes to the collector and emitter of the transistor by changing the polarity.
  • In both cases, the instrument will show infinity.

At discrepancy least one of the readings values ​​given in this manner, the transistor should be considered defective. For the structure of p-n-p all screening operations differ only polarity connection probes (pictured below).