How to check bipolar transistor multimeter

How to check bipolar transistor multimeter

Transistor. Damn, what a terrible word! I think we all dummies transistor is associated with something very difficult and confusing. But I assure you, my dear kettles, anything difficult is not present in the transistor. Let's first look at what he did it represents and how it can be checked for serviceability.

Immediately I say, in this article we will check bipolar transistors. What does it mean? So this is what These transistors consist of two P-N junctions. P-N transitions, holes, electrons bla bla bla. Well nafig! We do not need to know how to behave there electrons and the holes, etc. and etc. Just know if the current will flow through the P-N junction, he will be able to flow in only one direction. From P-N transition made by all the diodes. And as you know, the diode only passes current in one direction, and does not pass in the other direction. That is, in other words, in one direction, a small resistance of the diode, and the other - a very large. This is what we have seen with you in the article as a multimeter to test a diode.

Bipolar transistor, as I said, is composed of two P-N junctions. And depending on how the materials are placed P and N, and is called a transistor. The following figure is a schematic designation P-N-P transistor:

His conclusions are designated as the emitter, base and collector. The material which in the middle, between two other materials, called transistor base. Emitter and collector are on the edges and consist of one or of the same material. The P-N-P transistor current flows into the emitter and collects in the reservoir. A base current controls the current in the collector. It's simple :-). Schematic designation P-N-P transistor in the circuit is as follows:

where E - is the emitter, B - base, K - collector.

There is also another kind of bipolar transistor - N-P-N. There already material P is enclosed between the two materials N.

It works similar to the P-N-P transistor is simply the current flows in a different direction.

Here is his schematic representation of the diagrams

Since the diode is composed of one P-N junction, and the transistor of the two, it means you can imagine a transistor as two diodes! Eureka!

Now we are able to test transistor, checking these two diodes, of which, roughly speaking, is a transistor.

Well Well, let's practice determine the health of our transistor. And here is our patient:

Carefully read what we have written on the transistor: S4106. Now climb up to the Internet and search for document description on this transistor. In English it is called the datasheet. Directly and trying to drive in a search engine "C4106 datasheet". Note that import transistors written with English letters. But I datasheet it naryl: swing here.

We are most interested contacts pinout. That is, we need to know what the conclusion that it represents. To do this, the transistor, we need to find out where his base, where the emitter and the collector where. That's the beauty of the datasheet.

And here is the pinouts shemka:

Now it is clear to us that the first conclusion - it is the base, the second conclusion - a collector well and the third - the emitter.

We go back to our risunochki

Our ward - a N-P-N transistor. So, if he's healthy, we will have a small drop in voltage in millivolts, if we apply the "plus" to the database, and "minus" to the collector or emitter. And if we apply the "minus" to the database, and the "plus" to the collector or emitter, we see yedinichku on the cartoon. We begin checking transistor diodes, as we did when testing diodes in the article How to check diode multimeter.

We put on a dial and begin to thumb our transistor. To begin, set the "plus" to the database, and "minus" to the collector

Everything is OK, the direct P-N junction is to have a small voltage drop for silicon transistors 0.5-0.7 V and 0.3-0.4 volts for germanium. In the photo 543 millivolts or 0.54 volts.

Check the base-emitter putting on base, "plus" and on the emitter "minus".

We see again the voltage drop across the direct P-N junction. All OK.

Change probes places. We put a "minus" on the base, and "plus" to the collector. Now we are measuring the reverse voltage drop across the P-N junction.

Everything is OK, as we see yedinichku.

Now check the reverse voltage drop across the base-emitter.

Here we have a cartoon also shows yedinichku. So you can give the diagnosis transistor - healthy.

Let's check one more transistor. He is like a transistor, which we have examined. Its pinout (ie, the position and importance of the conclusions) is the same as our first hero. Also put a cartoon on a dial and tseplyaemya to our ward.

Tac-Toe. It is not good. This suggests that the P-N transition samples and once he knocked, then you can safely throw away such a transistor in the trash.

At the end of the article, I would like to add that it is always better to look for the datasheet on checking the transistor. There are so-called composite transistors. What does it mean? This means that in a constructive transistor body can be mounted two or more transistors or diodes along with the transistor together. Also keep in mind that some radioelements operate as transistors. It may be thyristors, stabilizers or voltage converters or even what some overseas mikroshemka. That's it! Do not be lazy to find datasheets on verifiable transistors.

How to check the transistor?

Checking transistor digital multimeter

Engaged in the repair and construction of electronics, often have to check on the serviceability of the transistor. Consider the control procedures as bipolar transistors ordinary digital multimeter, which is almost every novice hobbyists.

Despite the fact that the method of validation of a bipolar transistor is quite simple, novice amateur radio may sometimes encounter some difficulties. On peculiarities of testing bipolar transistors will be discussed a little later, but for now let us consider the simplest verification technology conventional DMM.

First you need to understand that a bipolar transistor can be conventionally represented as two diodes, as it consists of two p-n junctions. A diode is known, it is nothing more than a conventional p-n junction.

Here is a schematic diagram of a bipolar transistor, which will help to understand the principle of verification. Figure p-n transistor transitions are shown as semiconductor diodes.

Apparatus bipolar transistor p-n-p structure via diodes depicted as follows.

As is known, bipolar transistors are of two types of conductivity: n-p-n and p-n-p. This fact should be considered during the scan. Therefore show conditional equivalent transistor structure n-p-n made up of diodes. This figure we need in a subsequent verification.

The transistor structure n-p-n in the form of two diodes.

The essence of the method reduces to the verification of the integrity of the most p-n junctions, which are conditionally shown in the figure in the form of diodes. As you know, diode conducts current in one direction only. If you connect the plus ( + ) To a diode anode, and the minus (-) to the cathode, the p-n junction opens, and diode starts to conduct current. If you do just the opposite, to connect the plus ( + ) To the cathode of the diode, and a minus (-) to the anode, the p-n junction diode will be closed and will not pass current.

If suddenly during inspection found that the p-n junction conducts current in both directions, it means that he is "broken." If the p-n junction does not pass current in either direction, it means that the transition to the "cliff". It is natural that in case of breakdown or interruption of at least one of the p-n junctions transistor will not work.

Please note that schematic diagram of of diode is needed only for a visual representation of the transistor testing methodology. In reality, the transistor has a more sophisticated device.

Functional supports almost any multimeter diode test. The panel multimeter diode test mode is depicted in the form of a conditional image, which looks like this.

I think it is clear that we will check the transistor just using this feature.

A little explanation. In a digital multimeter has a few jacks for test leads. Three, or even more. When testing a transistor must be negative dipstick (the black) Connected to the jack COM (From the English. Word common - "common"), and the positive probe ( red ) Into the socket with the designation letter omega #&37;, letters V and possibly other letters. All depends on the functional unit.

Why do I tell such detail about how to connect the test leads to a multimeter? Because probes can then be easily confused and connect the black probe, which is conventionally considered a "minus" to the socket to which you want to connect the red, "plus" probe. As a result, this will cause confusion and, as a consequence of error. Be careful!

Now that the dry theory is described, move on to the practice.

What multimeter will use?

As a multi-function multimeter used multitester Victor VC9805 +, although suitable for measuring any digital tester, like all familiar DT-83x or MAS-83x. These multimeters can be purchased not only at radio, radio parts stores, but also in auto parts stores. Suitable multimeter can be bought on the Internet, for example, Aliekspress.

Initially spend checking silicon bipolar transistor domestic production KT503. It has a structure n-p-n. Here it pinout.

For those who do not know the meaning of this strange word pinout, I explain. Pinout - is the location of the functional findings on radioactive element housing. For functional transistor findings are manifold, respectively (TO or angl.- FROM), Emitter (E or angl.- E), Base (B or angl.- AT).

first connect red ( + ) Probe to the base of the transistor KT503 and the black (-) test lead to the conclusion that the reservoir. So we check the p-n transition work-Live (t. E. When the transition conducting). At the breakdown voltage appears. In this case, it is equal to 687 mV (687 mV).

Next, do not disconnect the red lead from the terminal base, connect black ( "negative") test lead to the conclusion that the emitter of the transistor.

As you can see, p-n junction between the base and emitter of the same conductive. The display again shows the breakdown voltage equal to 691 mV. Thus, we tested the transitions B-C and B-E under the direct inclusion.

To make sure of serviceability of p-n junctions of the transistor KT503 check them in, so called, The reverse inclusion. In this mode, the p-n junction does not conduct current, and should not be displayed display anything except "1". If the display unit "1"It means that the resistance of the junction is great, and it does not pass current.

To test the p-n transition B-To-B and E in the reverse inclusion, change the polarity of the probes to the terminals KT503 transistor. Negative ( "black") probe connects to the database, and the positive ( "red") first connects to the collector ...

... And then, without disconnecting the minus probe from the base output to the emitter.

As you can see from the photos, in both cases edinichka display the "1"Which, as already mentioned, it indicates that the p-n junction is not conducting. So we checked transitions B-C and B-E in The reverse inclusion.

If you have closely followed the exposition, we noticed that we had a transistor test according to the previously described method. As you can see, the transistor KT503 appeared undamaged.

If any of the crossings (B-C or B-E) are punched, then when checking the display multimeter found that they both ways, both direct inclusion, and to the contrary, do not show the breakdown voltage of the pn junction, and the resistance. This resistance is either zero "0" (will beep buzzer), or will be very small.

At breakage, p-n junction does not pass any current in the forward or in the opposite direction - the display in both cases will be "1". When such a defect p-n transition, as it were converted into an insulator.

Checking the bipolar transistor structure of p-n-p is analogous. But at the same time you must change the polarity connect the test leads to the terminals of the transistor. Recall schematic drawing of transistor p-n-p in the form of two diodes. If you forget it, take a look again and you will see that the cathodes of the diodes are connected together.

As a sample for our experiments we take domestic silicon transistor KT3107 structure p-n-p. Here it pinout.

In Pictures transistor scan will look like. We check the transition B-K for direct inclusion.

As we see, the transition is not defective. Multimeter showed breakdown voltage transition - 722 mV.

We do the same thing and to go to B-E.

As you can see, it is also OK. The display - 724 mV.

Now check the serviceability of the transition in the opposite direction - in the presence of a "breakdown" of the transition.

Transition B-K When you turn ...

Transition B-E in the reverse inclusion.

In both cases, the instrument display - edinichka "1". The transistor is OK.

To summarize and write out a brief check algorithm transistor digital multimeter:

Determination pinout transistor and its structure;

Check transitions B-To-B and E-Live using the diode test function;

Check transitions B-C and B-E to turn on the reverse (in the presence of a "breakdown") via the diode test function;

When testing is necessary to remember that in addition to conventional bipolar transistors, there are different versions of these semiconductor components. To those include composite transistors (transistors, Darlington), "digital" transistors, small transistors (so-called "strochniki"), etc.

They all have their own characteristics, such as built-in protection diodes and resistors. The presence of these elements in the transistor structure sometimes complicate them by using this technique. So before you check the unknown transistor, it is desirable to consult the documentation on him (datasheet). For information on how to find a datasheet for a specific electronic component or chip, I told here.

Takzhe You will be interested to know:

How to check the different types of transistors multimeter?

Semiconductor components are used in virtually all electronic circuits. Those who call them the most important and most widespread radio components are absolutely right. But any components do not last forever, over-voltage and current, violation of temperature and other factors can damage them. We tell (without overloading theory) as test efficiency of different types of transistors (npn, pnp, and polar compound) using a tester or multimeter.

Before a multimeter to check each item on the repair, whether a transistor, a thyristor, capacitor or resistor, it is necessary to determine its type and characteristics. You can do this on the label. On hearing it, will not be difficult to find the datasheet (datasheet) on the niche sites. With it, we will know the type of pinout, the main characteristics and other useful information, including analogues to replace.

For example, the TV stopped working scan. Suspected causes transistor line marked D2499 (by the way, quite a common case). Search the Internet for a specification (a fragment is shown in Figure 2), we obtain all the necessary information for testing.

Figure 2. Detail specification 2SD2499

Most likely, that will be found datasheet in English, do not worry, technical text easy to grasp, even without knowing the language.

After determining the type and pinout, desoldering item and proceed to checkout. Below are instructions with which we will test the most common semiconductor devices.

Checking bipolar transistor multimeter

This is the most common component, such as a series of KT315, KT361, etc.

With testing of this type of problem does not arise, it is sufficient to provide a pn junction diode in both. Then pnp and npn structure will have the form of two oppositely connected diodes, or back to a midpoint (see. Figure 3).

Figure 3. "Diode analogues" transitions pnp and npn

Join the multimeter test leads, black to "COM" (it will take), and the red jack «VΩmA» (plus). Turning on the testing device, we translate it in continuity or resistance measuring mode (it is sufficient to set a limit 2K Ohm), and proceed with the test. Let's start with pnp conductivity:

  1. Attach the black lead to the conclusion that the "B", and the red (from the nest «VΩmA») to the leg of the "E". We look at the testimony of a multimeter, it should display the value of resistance of the junction. The normal range of 0.6 ohms to 1.3 ohms.
  2. Likewise we perform measurement between the terminal "B" and "K". The reading should be in the same range.

If the first and / or second dimension multimeter displays minimal resistance, so the transition (s) of the sample and the item must be replaced.

  1. Changing the polarity (red and black lead) and repeat the measurement places. If the electronic component is defective, the displayed resistance tends to a minimum value. The indication is "1" (measured value exceeds the capabilities of the device), it is possible to ascertain the internal open circuit, therefore, require replacement radioelement.

Testing the reverse conduction device is produced by the same principle, with a slight variation:

  1. Red test connect to the leg of the "B" and check the resistance of the black probe (touching the terminals "C" and "E", in turn), it should be minimal.
  2. Changing the polarity and repeat measurements multimeter show resistance in the range of 0.6-1.3 kOhm.

Deviations from these values ​​indicate component malfunction.

Check FET performance

This type of semiconductor elements is also called mosfet and MOS components. Figure 4 shows a graphic notation n- and p-channel Polevikov in circuit diagrams.

Figure 4. Field effect transistors (N- and P-channel)

To test these devices connect to the multimeter test leads, in the same manner as in the test bipolar semiconductor type test and set "continuity test". Next, acting according to the following algorithm (for n-channel element):

  1. As for the black wire "with" legs, and red - O "and". Is displayed on the internal resistance of the diode, we remember reading.
  2. Now you need to "open" transition (succeed only partially) for this test lead to the red wire connects to the output "h".
  3. Repeat measurements carried out in para. 1, the indication will change in the smaller side, indicating a partial "opening" field workers.
  4. Now it is necessary to "close" the component for this purpose connect negative probe (black line) with the stalk "z".
  5. Repeat steps f. 1, displays an initial value, therefore, there was a "closure", which indicates the health of the component.

To test the elements of a p-channel-type sequence is the same, except for the polarity of the probe, it is necessary to change to the opposite.

Note that bipolar elements with insulated gate (IGBT), and tested as described above. Figure 5 shows SC12850 component relating to this class.

Figure 5. IGBT transistor SC12850

To test the need to follow the same steps as for the field of the semiconductor element, given that the drain and the source of the latter will correspond to the collector and emitter.

In some cases, the potential on the multimeter probes may not be enough (for example, to "discover" a strong power transistor), in such a situation will need extra food (enough for 12 volts). Connect it should be through the resistance of 1500-2000 ohms.

Checking the compound transistor

Such a semiconductor element is also called "Darlington Transistor", essentially two elements assembled in a single housing. For example, Figure 6 shows a portion of the specification to KT827A where it displayed an equivalent circuit of the device.

Figure 6. The equivalent circuit of the transistor KT827A

Check this item multimeter will not need to do a simple probe, it is shown in Figure 7.

Fig. 7. The circuit for checking composite transistor

  • T - test element, in this case KT827A.
  • L - light.
  • R - Resistor, its denomination is calculated by the formula h21E * U / I, i.e., multiply the input voltage value to the minimum value of the gain (for KT827A - 750), the result is divided by the load current. Suppose we use a light bulb taillights of the car 5W, the load current will be 0.42 A (5/12). Therefore, we need a 21 kOhm resistor (750 * 12 / 0.42).

Testing is performed as follows:

  1. Connects to the plus on the source, the result should be lighted lamp.
  2. Serve negative - light goes out.

This result suggests radio performance, while other results will need to be replaced.

How to check the unijunction transistor

As an example, KT117, a fragment of its specification is shown in Figure 8.

Figure 8. KT117, graphic image and an equivalent circuit

element check is carried out as follows:

Translate the multimeter to continuity test mode and check the resistance between the legs of "B1" and "B2", if it is small, it is possible to ascertain the breakdown.

How to check the transistor multimeter, not vypaivaya their scheme?

This question is quite relevant, especially in those cases where it is necessary to test the integrity of the smd components. Unfortunately, only the bipolar transistors can check not vypaivaya multimeter from the board. But even in this case can not be sure of the result, as is not uncommon, when the p-n junction element bypassed low-ohmic resistance.

There were cases when excessive force during brushing, brush damaged the transistor, a thyristor or another kompanent. . If a visual inspection of the returned no results, check the varistor multimeter for this desoldering.

Due to the difference in voltage levels and current in various modes, for their determination can be checked multimeter bipolar transistor, for example, a defective mode transistor gain.

How to check the different types of transistors multimeter? . How to check the thyristor multimeter? 06.23.2017. Electric, acoustic and sound insulation materials.

Electrical measurements. Select Page. How to check the PTC multimeter? . Unlike other electronic components (e.g., such as a transistor or a diode), a failed PTC resistor can often be identified by the appearance.

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