Schemes of testers of bipolar transistors. A device for testing any transistors Do-it-yourself power transistor testers

Probably there is no radio amateur who would not profess the cult of radio engineering laboratory equipment. First of all, these are attachments to them and probes, which are mostly self-made. And since there are never many measuring instruments and this is an axiom, I somehow assembled a small-sized and with a very simple circuit a tester for transistors and diodes. For a long time already there is not a bad multimeter, but a home-made tester, in many cases, I continue to use as before.

Device diagram

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

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

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

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

There are not many components of the circuit at all, but it is better to make a printed circuit board, it is troublesome to solder the 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 of a plastic case of a square battery, which has already worked out its own. All it took was to remove the previous contents and saw off the excess, drill holes for the LEDs and glue a bar with connectors for connecting the tested transistors. It will not be superfluous to “dress” the identification colors on the connectors. The power button is required. The power supply is a AAA battery compartment screwed to the case with several screws.

Mounting screws, small in size, are conveniently passed through the positive contacts and screwed with the obligatory use of nuts.

The tester is fully prepared. The best would be to use AAA batteries, four pieces of 1.2 volts will give the best option for a supplied voltage of 4.8 volts.

It allows you to measure the static current transfer coefficient of transistors of both structures at different values ​​of the base current, as well as the initial collector current. On this device, you can easily select pairs of transistors for the output stages of low-frequency amplifiers.

The current transfer coefficient is measured at base currents of 1, 3 and 10 mA, set respectively by the buttons S1, S2 and S3 (see figure). In this case, the collector current is counted on the scale of the PA1 milliammeter. The value of the static current transfer ratio is calculated by dividing the collector current by the base current. The maximum measured value of the parameter h 213 is 300. If the transistor is broken or a significant current flows in its collector circuit, the indicator lamps H1 and H2 light up.

The transistor under test is connected to the tester through one of the X1-X3 connectors. Connectors X2, X3 are designed for connecting medium power transistors - one or another of them is used depending on the location of the pins on the transistor case. To connector X1

turn on powerful transistors with flexible leads (but without plugs at the end). If the terminals of the transistor are rigid or flexible with plugs at the end, or it is installed on a radiator, an appropriate plug is inserted into connector X1 with three insulated stranded conductors, at the ends of which crocodile clips are soldered - they are connected to the transistor terminals. Depending on the structure of the tested transistor, switch S4 is set to the appropriate position.

Connector X1 - SG-3 (SG-5 is also possible), X2 and XZ are self-made made from a small-sized multi-pin connector (standard sockets for transistors are also suitable, of course). Push buttons S1-S3 - P2K, S4 - also P2K, but with a lock in the pressed position. Resistors - MLT-0.125 or MLT-0.25. Indicator lamps - МН2.5-0.15 (operating voltage 2.5 V, current consumption

0.15 A). Milliammeter RA 1 - for the current of the total deflection of the arrow 300 mA.

Details of the tester are placed in a case made of organic glass. Connectors X1-X3, switch S4, buttons S1, S3 and milliammeter RA1 are fixed on the front wall of the case. The remaining parts (including the power supply) are mounted inside the case. A sheet of paper with a grid is glued to the front panel to mark the collector current values ​​​​depending on the base current. The top sheet is covered with thin organic glass. The grid is used when constructing the characteristics of transistors, which are selected for the output stage of the bass amplifier. Characteristics are drawn on glass with a felt-tip pen or fountain pen, washed off with a damp swab.

Transistor testing begins with measuring the initial collector current with the base turned off. The PA1 milliammeter will show its value immediately after connecting the transistor leads to the connector. Then, pressing the S1 button, the collector current is measured and the static current transfer coefficient is determined. If the collector current is low, switch to another range by pressing the S2 or S3 button.

Magazine "Radio", 1982, No. 9, p.49

I want to share a circuit that is very useful for every radio amateur, found on the Internet and successfully repeated. This is really a very necessary device that has many functions and is assembled on the basis of an inexpensive ATmega8 microcontroller. There are a minimum of details, therefore, if there is a ready-made programmer, it is assembled in the evening.

This tester determines the numbers and types of outputs of a transistor, thyristor, diode, etc. with high accuracy. It will be very useful for both beginner radio amateurs and professionals.

It is especially indispensable in cases where there are stocks of transistors with half-erased markings, or if you can’t find a datasheet for some rare Chinese transistor. Scheme in the figure, click to enlarge or download the archive:

Types of tested radioelements

Element name - Display indication:

NPN transistors - display "NPN"
- PNP transistors - on the display "PNP"
- N-channel-enriched MOSFETs - on the display "N-E-MOS"
- P-channel-enriched MOSFETs - on the display "P-E-MOS"
- N-channel-depleted MOSFETs - on the display "N-D-MOS"
- P-channel-depleted MOSFETs - on the display "P-D-MOS"
- N-channel JFET - on the display "N-JFET"
- P-channel JFET - on the display "P-JFET"
- Thyristors - on the display "Tyrystor"
- Triacs - on the display "Triak"
- Diodes - on the display "Diode"
- Dual cathode diode assemblies - on the display "Double diode CK"
- Dual-anode diode assemblies - on the display "Double diode CA"
- Two series-connected diodes - on the display "2 diode series"
- Diodes symmetrical - on the display "Diode symmetric"
- Resistors - range from 0.5K to 500K [K]
- Capacitors - range from 0.2nF to 1000uF

Description of additional measurement parameters:

H21e (current gain) - range up to 10000
- (1-2-3) - the order of the connected pins of the element
- Presence of protection elements - diode - "Diode symbol"
- Forward voltage - Uf
- Opening voltage (for MOSFET) - Vt
- Gate capacitance (for MOSFET) - C=

The list provides an option to display information for the English firmware. At the time of this writing, Russian firmware appeared, with which everything became much clearer. to program the ATmega8 controller, click here.

The design itself is quite compact - about the size of a pack of cigarettes. Powered by a 9V "crown" battery. Current consumption 10-20mA.

For the convenience of connecting the tested parts, it is necessary to choose a suitable universal connector. And better a few - for various types of radio components.

By the way, many radio amateurs often have problems checking field-effect transistors, including those with an insulated gate. Having this device, you can in a couple of seconds find out its pinout, and performance, and junction capacitance, and even the presence of a built-in protective diode.

Planar smd transistors are also difficult to decipher. And many radio components for surface mounting sometimes fail even to roughly define - either it's a diode, or something else ...

As for conventional resistors, here the superiority of our tester over conventional ohmmeters, which are part of DT digital multimeters, is evident. Here, automatic switching of the required measuring range is implemented.

This also applies to testing capacitors - picofarads, nanofarads, microfarads. Simply connect the radio component to the device sockets and press the TEST button - all the basic information about the element will immediately be displayed on the screen.

The finished tester can be placed in any small plastic case. The device has been assembled and successfully tested.

Discuss the article TESTER OF SEMICONDUCTOR RADIO ELEMENTS ON THE MICROCONTROLLER

For transistors of the p-p-p structure, the polarity of switching on the supply battery GB and the measuring device RA must be reversed.

The reverse collector current Ikbo is measured at a given reverse voltage at the collector p-n junction and the emitter is off (Fig. 57, a). The smaller it is, the higher the quality of the collector junction and the stability of the transistor.

The parameter h21e, which characterizes the amplifying properties of the transistor, is defined as the ratio of the collector current Ik to the base current Ib that caused it, (Fig. 57, b), i.e. h2le ~ Ik / Iv. The larger the numerical value of this parameter, the greater the signal amplification that the transistor can provide.

To measure these two main parameters of low-power bipolar transistors, it can be recommended to make a prefix in a circle to the self-made avometer described above. The scheme of such a prefix is ​​shown in Fig. 58, a. The tested transistor V is connected by electrode leads to the corresponding terminals "E", "B" and "K" of the attachment, connected (through terminals XI, X2 and conductors with single-pole plugs at the ends) with a milliammeter of an avometer, switched on for a measurement limit of "1 mA". Switch S2 is preliminarily set to the position corresponding to the structure of the tested transistor. When checking a transistor of the p-r-p structure with the “Common.” the avometer is connected to the XI terminal of the attachment (as in Fig. 58, a), and when checking the transistor of the p-n-p structure, the X2 terminal is connected.

By setting the switch S1 to the "I KBO" position, the reverse current of the collector junction is measured first, and then, by switching the switch S1 to the "h21e" position, the static current transfer coefficient is measured. The deviation of the instrument pointer on the full scale when measuring the parameter I KB0 will indicate a breakdown of the collector junction of the transistor under test.

The h21e parameter is measured at a fixed base current, limited by resistor R1 to 10 μA. In this case, the transistor opens and in its collector circuit (including through a milliammeter) a current flows proportional to the coefficient h21e. If, for example, the device fixes a current of 0.5 mA (500 μA), then the coefficient h21e of the tested transistor will be 50 (500: 10 = 50). A current of 1 mA (deviation of the instrument needle to the end of the scale), therefore, corresponds to a coefficient h21e equal to 100. If the instrument needle goes off scale, the milliammeter of the avometer must be switched to the next current measurement limit - “10 mA”. In this case, the entire scale of the device will correspond to a coefficient h21e equal to 1000, and every tenth of it will correspond to 100.

Resistor R2, which limits the current in the measuring circuit to 3 mA, is needed to prevent damage to the measuring device due to breakdown of the transistor under test.
A possible design of the attachment is shown in Fig. 58b. For the front panel, approximately 130X75 mm in size, it is advisable to use sheet getinax or textolite 1.5-2 mm thick.

Clamps "E", "B" and "K> for connecting the terminals of the transistor of the "crocodile" type. The switch for the type of measurements S1 is a toggle switch TP2-1, the structure of the transistor S2 is TP1-2. The GB1 - 3336L power battery or composed of three 332 elements is mounted on the panel from below, and limiting resistors R1 and R2 are also mounted there. Clamps (or sockets) for connecting the attachment to the avometer are placed in any convenient place, for example, on the back side wall of the box. On top of the panel, a brief instruction for working with the measuring attachment is glued. You can check the performance and evaluate the amplifying properties of transistors of medium and high power using a simple device, the circuit of which is shown in Fig. 59. The tested transistor V is connected to the terminals corresponding to its electrodes. In this case, the ammeter RA1 is connected to the collector circuit of the transistor for the current of the total deflection of the arrow 1A, and one of the resistors R1-R4 is connected to the base circuit. The resistances of the resistors are selected so that the current of the base circuit of the transistor can be set equal to 3, 10, 30 and 50 mA. Thus, the transistor test is carried out at fixed currents in the base circuit, set by switch S1. The power source is three elements 373 connected in series, or a low-voltage rectifier that provides a voltage of 4.5 V at a load current of up to 2A.

The numerical value of the static current transfer coefficient of the tested transistor is determined as the ratio of the collector current to the base current that caused it. For example, if the switch S1 is set to a base current of 10 mA, and the ammeter PA 1 records a current of 500 mA, then the coefficient h21e of this transistor is 50 (500: 10 = 50).

The design of such a device - a transistor tester is arbitrary. It can be made as an attachment to an avometer, the ammeter of which is designed to measure direct currents up to several amperes.

It is necessary to check the transistor as soon as possible, because already at a collector current of 250 ... 300 mA it starts to heat up and thereby introduce errors into the measurement results.

It is desirable to have a medium and high power transistor tester in a radio amateur's measuring laboratory. It is especially necessary when selecting pairs of transistors for terminal push-pull cascades of audio frequency amplifiers with a power of more than 0.25 W.

The proposed device can be tested for breakdown of the collector junction of the transistor, measure the static current transfer coefficient h21e, check the stability of the transistor. Tests are carried out when the transistor is turned on according to the circuit with a common emitter. The indicator is a milliammeter for a current of 1 mA. The power source is a rectifier that provides a constant voltage of 12 V at a current of up to 300 mA. The reverse current of the Irbo collector junction is not measured, since for different transistors it can be from several microamperes to 12 ... 15 mA and this parameter has practically no effect on the selection of pairs of transistors for operation in a power amplifier.

The schematic diagram of the device is shown in fig. 1. The transistor VT to be tested is connected with the leads of the electrodes to the corresponding terminals of the device. Switch SA1 sets the structure of the transistor. In this case, a power source is connected to the transistor in polarity corresponding to its structure. Next, the transistors are checked, observing the following order: the collector junction is checked for breakdown; set the base current Ib equal to 1 mA; measure the static current transfer coefficient h 21e

Measurements of these parameters of medium and high power transistors illustrate the circuits shown in fig. 2.

The collector transition is tested by pressing the SB2 Breakdown button. At the same time, resistor R4 and milliammeter RA1 are included in the collector circuit of the tested transistor VT, the negative terminal of which is connected to the power source, and resistors Rl - R3 are connected in parallel to the collector junction (Fig. 2, a).

At this time, the sliders of the variable resistors R2 and R3 should be in the right (according to the diagram) position. The strength of the current flowing through the chain of resistors Rl - R3 does not exceed 50 μA, which practically does not affect the readings of the milliammeter. Resistor R4 limits the current through the milliammeter to 1 mA, thereby preventing its needle from going off scale in the event of a breakdown of the collector junction of the transistor.

Milliammeter readings less than 1 mA indicate that the collector junction is working, and when it breaks down, the milliammeter needle will always be set to the extreme right division of the scale. In the event of a break between the terminals of the collector and base electrodes, the device will only show the current passing through the resistors Rl - R4.

The base current /b, equal to 1 mA, is set by resistors R3 Coarsely and R2 Exactly with the SB2 button pressed. In this case, an insignificant initial collector current and current through the resistors Rl - R3 flow through the milliammeter (Fig. 2, b), which, when measuring the h21e coefficient, will be the base current Ib of the transistor under test.

The static current transfer coefficient is measured by pressing the SB4 h21e 300 button or, with a small numerical value of this parameter, the SB3 h21e 60 button. In this case, the button contacts connect the emitter of the transistor to the positive (or negative, if the transistor of the p-p-p structure) conductor of the power source, and parallel to the milliammeter - a wire resistor R5 (or R6), expanding the measurement limit (Fig. 2, c). The collector current of the transistor under test will approximately correspond to its static current transfer ratio. The error arising from the simplification of switching circuits of the device does not affect the selection of pairs of transistors for the output stages of powerful AF amplifiers.

When testing transistors of the p-p-p structure, a milliammeter is included in the circuit of its emitter,

The design of the device is optional. Resistors R1 and R4 type MLT-0.5, R2 and R3 - SP-3. Resistors R5 and R6 are made from high resistivity wire with a diameter of 0.4 ... 0.5 mm. Switch SA1 - toggle switch TP1-2, pushbutton switches SB1 - SB4-KM2-1. Power-on indicator HL1 - switching lamp KM24-90 (24 Vx90 mA).

By selecting the resistor R4 with the collector and base clamps short-circuited and the SB2 button pressed, the milliammeter needle is set as accurately as possible to the extreme right division of the scale.

To adjust the resistances of resistors R5 and R6, you will need an exemplary milliammeter for a current of 300 ... 400 mA and variable wire resistors with a resistance of 51 ... 62 and 240 ... 300 Ohms. An exemplary milliammeter, a transistor tester milliammeter, a resistor R5 and a variable resistor of 51 .... 62 Ohms are connected in series. Turning on the power source, a variable resistor sets a current in the circuit equal to 300 mA, while at the same time making sure that the milliammeter needle of the device does not go off scale. After that, by adjusting the resistance of the resistor R5, the arrow of the milliammeter of the device is set to the extreme right division of the scale. Then the variable resistor is replaced with a resistor with a resistance of 240 ... 300 Ohms, the resistor R5 with a resistor-R6 and in the same way the current is set to 60 mA in the circuit, and the arrow of the milliammeter of the device is set to the extreme right mark of the scale.

When the SB4 button is pressed, the deviation of the arrow of the tester's milliammeter on the full scale corresponds to the static current transfer coefficient of the transistor 300, while the SB3 button is pressed - 60.