Transistor- This is a very important element of most radio circuits. Those who decide to engage in radio modeling must first of all know how to test them and what devices to use.

A bipolar transistor has 2 PN junctions. The outputs from it are called emitter, collector and base. The emitter and collector are elements located at the edges, and the base is located between them, in the middle. If we consider the classical scheme of current movement, then it first enters the emitter and then accumulates in the collector. The base is necessary in order to regulate the current in the collector.

Step-by-step instructions for checking with a multimeter

Before starting the test, first of all, the structure of the triode device is determined, which is indicated by the emitter junction arrow. When the direction of the arrow points towards the base, then this is the PNP variant, the direction opposite to the base indicates NPN conductivity.

Multimeter check PNP transistor consists of the following sequential operations:

1. Checking the reverse resistance, to do this, we attach the “positive” probe of the device to its base.
2. The emitter junction is tested, for this we connect the “negative” probe to the emitter.
3. To check the collector move the negative probe onto it.

The results of these measurements should show a resistance within the value of “1”.

To check direct resistance, swap the probes:

1. "Minus" We attach the probe of the device to the base.
2. "Plus" We move the probe one by one from the emitter to the collector.
3. On the multimeter screen resistance indicators should be from 500 to 1200 Ohms.

These readings indicate that the transitions are not broken, the transistor is technically sound.

Many amateurs have difficulty identifying the base, and, accordingly, the collector or emitter. Some advise starting to determine the base, regardless of the type of structure, in this way: alternately connecting the black probe of the multimeter to the first electrode, and the red probe alternately to the second and third.

The base will be detected when the voltage across the device begins to drop. This means that one of the transistor pairs has been found - “base-emitter” or “base-collector”. Next, you need to determine the location of the second pair in the same way. The common electrode of these pairs will be the base.

Instructions for checking with a tester

Testers differ by type of model:

1. There are devices, in which the design provides devices that allow measuring the gain of low-power microtransistors.
2. Regular testers allow testing in ohmmeter mode.
3. Digital tester measures the transistor in test mode.

In any case, there is a standard instruction:

1. Before you start checking, it is necessary to remove the charge from the shutter. This is done like this: literally for a few seconds the charge must be short-circuited with the source.
2. In the case when a low-power field-effect transistor is tested, then before you pick it up, you must remove the static charge from your hands. This can be done by holding your hand on something metal that has a ground connection.
3. When tested with a standard tester, you must first determine the resistance between drain and source. In both directions it should not make much difference. The resistance value with a working transistor will be small.
4. Next step– measurement of the junction resistance, first direct, then reverse. To do this, you need to connect the tester probes to the gate and drain, and then to the gate and source. If the resistance in both directions is different, the triode device is working properly.

How to test a transistor without desoldering it from the circuit

Probe circuit for testing transistors: R1 20 kOhm, C1 20 μF, D2 D7A - Zh.

Soldering a certain element from the circuit is associated with some difficulties - according to appearance It is difficult to determine which one needs to be soldered.

Many professionals suggest using a probe to test the transistor directly in the socket. This device is a blocking generator, in which the role of the active element is played by the part itself that requires testing.

Probe operation system with complex circuit is built on the inclusion of 2 indicators that indicate whether the circuit is broken or not. Options for their manufacture are widely presented on the Internet.

The sequence of actions when checking transistors with one of these devices is as follows:

1. First, a working transistor is tested, with the help of which they check whether there is current generation or not. If there is generation, then we continue testing. In the absence of generation, the winding terminals are swapped.
2. Next, lamp L1 is checked for open circuit probes. L The lamp should be on. If this does not happen, the terminals of any of the windings are swapped.
3. After these procedures The device begins a direct check of the transistor that is supposedly out of order. Probes are connected to its terminals.
4. The switch is installed to the PNP or NPN position, the power is turned on.

The glow of lamp L1 indicates the suitability of the circuit element being tested. If lamp L2 starts to light, then there is some problem (most likely the junction between the collector and the emitter is broken);

If none of the lamps lights up, then this is a sign that it is out of order.

There are also samples with very simple circuits, which do not require any adjustment before starting work. They are characterized by a very small current that passes through the element to be tested. At the same time, the danger of its failure is practically zero.

To check, you need to perform the following operations sequentially:

1. To plug one of the probes to the most likely output of the base.
2. The second probe We touch each of the remaining two conclusions in turn. If there is no contact in one of the connections, then an error occurred with the selection of the base. You need to start over with a different order.
3. Next, it is advised to perform the same operations with another probe.(change positive to negative) on the selected base.
4. Alternate base connection using probes of different polarities with the collector and emitter, in one case it should make contact, but in the other not. It is believed that such a transistor is working.

Main causes of malfunction

The most common reasons for the triode element to fail to operate in electronic circuit the following:

1. Transition break between components.
2. Breakdown one of the transitions.
3. Breakdown collector or emitter section.
4. Power leak under circuit voltage.
5. Visible damage conclusions.

Characteristic external signs Such failures include blackening of the part, swelling, and the appearance of a black spot. Since these shell changes only occur with powerful transistors, then the issue of diagnosing low-power remains relevant.

1. There are many ways determination of the malfunction, but first you need to understand the structure of the element itself, and clearly understand the design features.
2. Selecting a device for testing- This important point regarding the quality of the result. Therefore, if you lack experience, you should not limit yourself to improvised means.
3. While checking, you should clearly understand the reasons for the failure of the tested part, so as not to return over time to the same state of failure of household electrical appliances.

This article will present, in my opinion, the simplest, but no less effective circuit of Field Mice (field-effect transistors). I think this circuit will rightfully take one of the leading positions on the Internet in terms of simplicity and reliability of assembly. Since there is simply nothing to shake or burn here... The number of parts is minimal. Moreover, the circuit is not critical to the ratings of the parts... And can be assembled practically from rubbish, without losing its functionality...

Many will say, why some kind of probe for transistors? If everything can be checked with a regular multimeter... And to some extent they will be right... To assemble a probe you need to at least have a soldering iron and a tester... To check the same diodes and resistors. Accordingly, if there is a tester, then a probe is not needed. Yes and no. Of course, you can check a field-effect transistor (field-effect mouse) for functionality with a tester (multimiter) ... But it seems to me that this is much more difficult to do than checking the same field-effect mouse with a probe ... I will not explain in this article how a field-effect mouse (field-effect transistor) works. So, for a specialist this has all been known for a long time and is not interesting, but for a beginner everything is complicated and complicated. So it was decided to do without boring explanations of the principle of operation of a field mouse ( field effect transistor).

So, the probe circuit, and how they can test a field-effect mouse (field-effect transistor) for survivability.

We assemble this circuit, even on a printed circuit board (the seal is attached at the end of the article). At least mounted installation. Resistor values ​​can differ by about 25% in either direction.

Any button without locking.

The LED can be either bipolar, two-color, or even two back-to-back parallel. Or even just one. If you plan to test transistors of only one structure.. Only N channel type or only P channel type.

The diagram is assembled for field mice of the N channel type. When checking P channel type transistors, you will have to change the polarity of the circuit power supply. Therefore, another counter LED was added to the circuit, parallel to the first one.. In case you need to check a field mouse (field effect transistor) P channel type.

Many will probably immediately notice that the circuit does not have a power polarity switch.

This was done for several reasons.

1 No such suitable switch was available.

2 Just so as not to get confused in what position the switch should be when checking the corresponding transistor. I get N channel transistors more often than P channel ones. Therefore, if necessary, it is not difficult for me to simply swap the wiring. To test P channel field mice (field effect transistors).

3 Just to simplify and reduce the cost of the scheme.

How does the scheme work? How to test field mice for survivability?

We assemble the circuit and connect the transistor (field mouse) to the corresponding terminals of the circuit (drain, source, gate).

Without pressing anything, connect the power. If the LED doesn't light up, it's already good.

If at correct connection transistor to the probe, power supply and the button NOT pressed, the LED will light up... This means the transistor is broken.

Accordingly, if the button is pressed, the LED does NOT light up. This means the transistor is broken.

That's the whole trick. Everything is brilliantly simple. Good luck.

P/S. Why in the article do I call a field-effect transistor a field mouse? Everything is very simple. Have you ever seen transistors in a field? Well... Simple. Do they live there or grow there? I think no. But there are field mice... And here they are more appropriate than field-effect transistors.

And why are you surprised by the comparison of a field-effect transistor with a field-effect mouse? After all, there is, for example, the site radiokot or radioskot. And many other sites with similar names.. Which have nothing to do directly with living creatures... So.

I also think that it is quite possible to call a bipolar transistor, for example, a polar polar bear...

And I also want to express my deep gratitude to the author of this probe circuit, V. Goncharuk.

There is probably no radio amateur who does not profess the cult of radio engineering laboratory equipment. First of all, these are attachments for them and probes, which for the most part are made independently. And since there are never too many measuring instruments and this is an axiom, I somehow assembled a transistor and diode tester that was small in size and had a very simple circuit. It’s been a long time since I’ve had a multimeter that’s not bad, but homemade tester, in many cases, I continue to use it as before.

Device diagram

The probe designer consists of only 7 electronic components + printed circuit board. It assembles quickly and starts working absolutely without any setup.

The circuit is assembled on a chip K155LN1 containing six inverters. When the leads of a working transistor are correctly connected to it, one of the LEDs lights up (HL1 for the N-P-N structure and HL2 for the P-N-P structure). If faulty:

1. broken, both LEDs flash
2. has an internal break, both do not ignite

The diodes being tested are connected to terminals “K” and “E”. Depending on the polarity of the connection, HL1 or HL2 will light up.

There are not many circuit components, but it’s better to make them printed circuit board, it is troublesome to solder wires to the legs of the microcircuit directly.

And try not to forget to put a socket under the chip.

You can use the probe without installing it in the case, but if you spend a little more time on its manufacture, you will have a full-fledged, mobile probe that you can already take with you (for example, to the radio market). The case in the photo is made from the plastic case of a square battery, which has already served its purpose. All that was needed was to remove the previous contents and saw off the excess, drill holes for the LEDs and glue a strip with connectors for connecting the transistors being tested. It would be a good idea to “dress” the connectors with identification colors. A power button is required. The power supply is a AAA battery compartment screwed to the case with several screws.

The fastening screws are small in size, it is convenient to pass them through the positive contacts and tighten them with the obligatory use of nuts.

The tester is in full readiness. It would be optimal to use AAA batteries; four 1.2 volt batteries will give the best supply voltage of 4.8 volts.

Such useful amateur radio probes are convenient because they have a simple design, contain a minimum of elements and are at the same time universal - you can quickly check the performance of almost any widely used transistors (except field-effect ones) and audio or RF stages.

Transistor probes

Below are two transistor probe circuits. They are the simplest self-oscillators, where the transistor being tested is used as an active element. The peculiarity of both circuits is that they can be used to test transistors without removing them from the circuit. You can also use this probe to determine the pinout and structure (p-n-p, n-p-n) of transistors unknown to you experimentally, simply by alternately connecting its probes to different terminals of the transistor. If the transistor is in working order and connected correctly, it will sound sound signal. You will not damage any transistor, even a low-power one (if it is turned on incorrectly), since the currents during testing are very small and limited by other elements of the circuit. The first circuit with a transformer:

A similar transformer can be taken from any old pocket transistor receiver, for example, “Neva”, “Selga”, “Sokol” and the like (this is a transition transformer between the stages of the receiver, and not the one that is at the output of the speaker!). In this case, the secondary winding of the transformer (it has a middle terminal) must be reduced to 150 - 200 turns. The capacitor can have a capacity of 0.01 to 0.1 µF, and only the tone of the sound will change when tested. If the transistor being tested is working properly in the telephone capsule connected to the second winding of the transformer, a sound will be heard.

The second probe is transformerless, although the principle of operation is similar to the previous scheme:

The probe is assembled in a suitable small-sized housing. There are few parts and the circuit can be soldered by surface mounting, directly on the switch contacts. Battery type "Krona". Switches - with two groups of contacts for switching, for example, type “P2-K”. The “Emitter”, “Base” and “Collector” probes are wires of different colors (it is better to make sure that the letter of the wire color matches the output of the transistor. For example: collector - red or brown, base - white, emitter - any other color). This will make it more convenient to use. You need to solder lugs onto the ends of the wires, for example from wire or thin long nails. You can solder the wire to the nail using a simple aspirin tablet (acetylsalicylic acid). As a sound emitter, you should take a high-impedance telephone capsule (such as “DEMSh” or, for example, from the handset of old types of devices), because their sound volume is quite high. Or use high-impedance headphones.

I personally have been using a transistor probe assembled according to this circuit for many years and it really works without any complaints. You can test any transistors - from micropower to high power. But you shouldn’t leave the probe with the battery turned on for a long time, because the battery will quickly run out. Since I assembled the circuit many years ago, germanium transistors of the MP-25A type (or any of the MP-39, -40, -41, -42 series) were used.

It is quite possible that modern silicon transistors will be suitable, but I personally have not tested this option in practice. That is, the circuit will, of course, be operational as a generator, but I find it difficult to say how it will behave when testing transistors without desoldering them from the circuit. Because the opening current of germanium elements is less than that of silicon elements (such as KT-361, KT-3107, etc.).

For these purposes, you can make a very simple multivibrator probe using two transistors.

With this probe you can quickly find a faulty cascade or active element (transistor or microcircuit) in a non-working circuit. When checking audio stages (amplifiers, receivers, etc.), its X2 probe must be connected to the common wire (GND) of the circuit being tested, and the X1 probe must alternately touch the output and input points of each stage, starting from the output of the entire device. The service/failure indicator in this case is the speaker (or headphones) of the device being tested. For example, we first apply a signal to the input of the final stage (the power of the device under test must be turned on!) and if there is sound in the speaker, then the output stage is working. Then we touch the input of the pre-terminal stage with the probe, etc., moving towards the input stages of the device. If there is no sound in the speaker at any of the cascades, then this is where you should look for the problem.

Due to the simplicity of the circuit, this probe-generator, in addition to the fundamental frequency (about 1000 Hz), also produces numerous harmonics that are multiples of the fundamental frequency (10, 100, ... kHz). Therefore, it can also be used for high-frequency stages, for example, receivers. Moreover, in this case, probe X2 does not even have to be connected to the common wire of the device being tested; the signal will be supplied to the stages being tested due to capacitive coupling. When checking the functionality of a receiver with a magnetic antenna, it is enough to bring probe X1 closer to the antenna. Structurally, this probe can be made on a board made of foil PCB and look like this:

As on/off For power supply, you can use a microswitch (microphone, button) without fixing. Then power will be supplied to the multivibrator when this button is pressed. Author of the article: Baryshev A.

The need for such a device arises every time when repairing a welding inverter– you need to check a powerful IGBT or MOSFET transistor for serviceability, or select a pair for a working transistor, or when purchasing new transistors, make sure that it is not a “remarker”. This topic has been repeatedly raised on many forums, but having not found a ready-made (tested) or someone designed device, I decided to make it myself.
The idea is that you need to have some kind of database various types transistors, with which to compare the characteristics of the transistor under test, and if the characteristics fit within a certain framework, then it can be considered serviceable. All this should be done using some simplified method and simple equipment. Of course, you will have to collect the necessary database yourself, but this can all be solved.

The device allows:
- determine the serviceability (failure) of the transistor
- determine the gate voltage required to fully open the transistor
- determine the relative voltage drop across K-E conclusions open transistor
- determine the relative gate capacitance of the transistor, even in one batch of transistors there is a scatter and it can be seen indirectly
- select several transistors with the same parameters

Scheme

The schematic diagram of the device is shown in the figure.

It consists of a 16V power supply direct current, digital millivoltmeter 0-1V, voltage stabilizer +5V on LM7805 to power this millivoltmeter and power the “light clock” - flashing LED LD1, current stabilizer on the lamp - to power the transistor under test, current stabilizer to - to create adjustable voltage(at a stable current) on the gate of the transistor under test using a variable resistor, and two buttons to open and close the transistor.

The device is very simple in design and is assembled from publicly available parts. I had some kind of transformer with an overall power of about 40 W and a voltage on the secondary winding of 12 V. If desired, and if necessary, the device can be powered from a 12V / 0.6 Ah battery (for example). It was also in stock.

I decided to use power from a 220V network, because you can’t go to the market for shopping with the device, and the network is still more stable than a “dead” battery. But... it's a matter of taste.
Further, while studying and adapting the voltmeter, I discovered an interesting feature: if a voltage exceeding its upper measurement threshold (1V) is applied to its terminals L0 and HI, then the display simply goes out and it does not show anything, but if you reduce the voltage and everything returns to normal indication (this is all with a constant supply of +5V between terminals 0V and 5V). I decided to use this feature. I think that many digital “display meters” have the same feature. Take, for example, any Chinese digital tester, if in 20V mode you apply 200V to it, then nothing bad will happen, it will just display “1” and that’s it. Scoreboards similar to mine are now on sale.
Possible.

About the operation of the circuit

Next, I’ll tell you about four interesting points about the scheme and its operation:
1. The use of an incandescent lamp in the collector circuit of the transistor under test is due to the desire (initially there was such a desire) to visually see that the transistor has OPENED. In addition, the lamp performs 2 more functions here: protecting the circuit when connecting a “broken” transistor and some stabilization of the current (54-58 mA) flowing through the transistor when the network changes from 200 to 240V. But the “feature” of my voltmeter allowed me to ignore the first function, while even gaining in measurement accuracy, but more on that later...
2. The use of a current stabilizer made it possible NOT to accidentally burn out a variable resistor (when it is in the top position according to the circuit) and accidentally press two buttons at the same time, or when testing a “broken” transistor. The amount of limited current in this circuit even with short circuit equal to 12 mA.
3. Using 4 pieces of IN4148 diodes in the gate circuit of the transistor under test to slowly discharge the gate capacitance of the transistor when the voltage at its gate has already been removed and the transistor is still in the open state. They have some insignificant leakage current, which discharges the capacitance.
4. Use of a “blinking” LED as a time meter (light clock) when the gate capacitance is discharged.
From all of the above, it becomes absolutely clear how everything works, but more on this a little later...

Housing and layout

Next, a case was purchased and all these components are located inside.

Outwardly, it turned out not even bad, except for the fact that I still don’t know how to draw scales and inscriptions on a computer, but... The remains of some connectors worked great as sockets for the transistors under test. At the same time, an external cable was made for transistors with “clumsy” legs that would not fit into the connector.

Well, this is what it looks like in action:

How to use the device

1. We turn on the device into the network, the LED starts blinking, the “display meter” does not light up
2. Connect the transistor under test (as in the photo above)
3. Set the voltage regulator knob on the gate to the extreme left position (counterclockwise)
4. Press the “Open” button and at the same time slowly increase the voltage regulator clockwise until the “display meter” lights up
5. Stop, release the “Open” button, take readings from the regulator and record. This is the opening tension.
6. Turn the regulator all the way clockwise
7. Press the “Open” button, the “display meter” will light up, take readings from it and record it. It's there K-E voltage on an open transistor
8. It is possible that during the time spent on recording, the transistor has already closed, then we open it again with the button, and after that we release the “Open” button and press the “Close” button - the transistor should close and the “display meter” should go out accordingly. This is a check of the integrity of the transistor - it opens and closes
9. Again, open the transistor with the “Open” button (voltage regulator at maximum) and, having waited for the previously recorded readings, release the “Open” button while simultaneously starting to count the number of flashes (blinks) of the LED
10. After waiting for the “display meter” to go out, we record the number of LED flashes. This is the relative time of discharge of the transistor's gate capacitance or closing time (until the voltage drop across the closing transistor increases by more than 1V). The greater this time (quantity), the correspondingly greater the gate capacity.

Next, we check all the available transistors, and put all the data in a table.
It is from this table that it comes comparative analysis transistors - whether they are branded or “remarkers”, whether they correspond to their characteristics or not.

Below is the table that I came up with. Transistors that were not available are highlighted in yellow, but I definitely used them once, so I left them for the future. Of course, it doesn’t represent all the transistors that passed through my hands; I simply didn’t write down some of them, although I seem to always write. Of course, when repeating this device, someone may end up with a table with slightly different numbers, this is possible, because the numbers depend on many things: on the existing light bulb or transformer or battery, for example.

The table shows the difference between transistors, for example G30N60A4 from GP4068D. They differ in closing time. Both transistors are used in the same device - Telvin, Technique 164, only the first ones were used a little earlier (3, 4 years ago), and the second ones are used now. And the rest of the characteristics according to DATASHIT are approximately the same. And in this situation, everything is clearly visible - everything is there.

In addition, if you have a table of only 3-4 or 5 types of transistors, and the rest are simply not available, then you can probably calculate the coefficient of “consistency” of your numbers with my table and, using it, continue your table using numbers from my table. I think that the dependence of “consistency” in this situation will be linear. For the first time, it will probably be enough, and then you will adjust your table over time.
I spent about 3 days on this device, one of which was buying some small things, a housing, and another one for setting up and debugging. The rest is work.

Of course, the device has possible design options: for example, using a cheaper pointer millivoltmeter (you need to think about limiting the pointer's travel to the right when the transistor is closed), using another stabilizer instead of a light bulb, using a battery, installing an additional switch to test transistors with a p-channel, etc. .d. But the principle in the device will not change.

I repeat once again, the device does not measure the values ​​(digits) indicated in the DATASHEETS, it does almost the same thing, but in relative units, comparing one sample to another. The device does not measure characteristics in dynamic mode, it is only static, like a regular tester. But not all transistors can be checked with a tester, and not all parameters can be seen. On these I usually put a question mark “?”

You can also test it in dynamics, put a small PWM on the K176 series, or something similar.
But the device is generally simple and inexpensive, and most importantly, it ties all subjects to the same framework.

Sergey (s237)

Ukraine, Kyiv

My name is Sergey, I live in Kyiv, age 46 years. I have my own car, my own soldering iron, and even my own workplace in the kitchen, where I sculpt something interesting.

I love high-quality music on high-quality equipment. I have an ancient Technix, everything sounds on it. Married, has adult children.

Former military. I work as a master repairing and adjusting welding equipment, including inverter equipment, voltage stabilizers and much more, where electronics are present.

I don’t have any special achievements, except that I try to be methodical, consistent and, if possible, finish what I start. I came to you not only to take, but also, if possible, to give, to discuss, to talk. That's all briefly.

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