check transistor performance technology

Preparation tools

Eachmodern ham is a universal tool called digital multimeter.It allows you to measure the constant and variable currents and voltage, resistance elements.It also allows you to test the functionality of the circuit elements.Near the switch in the "continuity" mode typically drawn diode and speaker (see. The photo on Fig. 1).

Figure 1 - Front panel multimeter

before checking element is necessary to ensure performance of the meter:

1. battery must be charged.
2. When you switch to scan mode semiconductor display must show the figure 1.
3. Probes are undamaged, that is, to the majority of instruments -.. The Chinese, and the wire in them is a very frequent occurrence.Check them need the tips of leaning probes to each other: in this case, the display shows zeros and you will hear a beep - the unit and the probes are intact.
4. probes are connected according to the color coding: red lead - red connector, black - black connector labeled COM.

If you do not know how to use this product, be sure to read detailed instructions for dummies on how to use a multimeter!

Technology verification

Bipolar

structure of the bipolar transistor (BT) includes two p-n or 2 n-p junction.The conclusions of these transitions are called the emitter and collector.The output of the core layer is called the base.Simplistically BT can be represented as two included counter diode, as shown in Figure 2.

Figure 2 - NPN diode model and its "analog»

Check bipolar transistor multimeter is not difficult, what you now see.As you know the basic property of p-n transition is its unilateral conductivity.When you connect the positive (red) probe to the anode, the cathode and black to display the meter will display the value of the forward voltage across the junction in millivolts.The voltage depends on the type of semiconductor: germanium diodes for this voltage is of the order of 200-300 mV, and for silicon from 600 to 800 mV.In the opposite direction diode current does not pass, so if you change probes places, it will be displayed on the display 1, indicating an infinite resistance.

If diode "broken", then most likely you will hear a beep, and in both directions.If the diode "in breakage" on the display, and will display unit.

Thus, the essence of the test if the transistor is in the "continuity» p-n junctions base-collector, the base-emitter and emitter-collector forward and reverse inclusion:

• base-collector: Red test lead connects to the black to the collector.Compound should work as a diode and conduct current in one direction only.
• base-emitter: The red probe is connected to the base, black connects to the emitter.Similar to the previous point connection should conduct current only when Live.
• emitter-collector: Do-good transition resistance of this area tends to infinity, which will speak on the display unit.

analogue will also look During the function test "diode» pnp type, but the diodes are connected opposite.In this case, the black plug connects to the database.Move the emitter-collector verified similarly.

Field

Field effect transistors (FET) or "field workers" are used in power supplies, monitors, audio-visual equipment.Therefore, the need to test more often faced master equipment repair.Independently verify the element can also be with a conventional multimeter at home.

Figure 3 is a block diagram of PT.Conclusions Gate (gate), Drain (drain), Source (the source) can be arranged in different ways.Very often manufacturers label their letters.If marks are absent, it is necessary to consult the reference data, pre-learning model name.

Figure 3 - Structural PT

scheme should be borne in mind that the repair of equipment, which are PT, often arises the problem of checking the health and integrity without watering member of the board.More often than not fail powerful FETs to be installed in switching power supplies.It should also be remembered that the "field workers" are extremely sensitive to static discharge.Therefore, before you check the FET vypaivaya not need to wear an antistatic wrist strap and observe safety precautions.

Figure 4 - Wrist strap

Check PT multimeter can be similar to the continuity of the bipolar transistor junctions.At serviceable "field workers" between terminals - infinite resistance, regardless of the applied test voltage.However, there are some exceptions: if you put the positive probe of the tester to the gate, and the negative - to the source, the charge capacity of the breech, and the transition will be opened.When measuring the resistance between the drain and source of the meter may show some resistance value.Inexperienced masters often take this phenomenon as a sign of failure.However, this does not always correspond to reality.It is necessary to check the channel drain-source short-circuit all the terminals PT to discharge the junction capacitance.Thereafter, they again become large resistance, and can be re-checked or not operating the transistor.If this procedure does not work, then the item is considered to be non-functional.

Composite

types of composite transistor or a Darlington circuit is shown in Figure 5. These two elements are arranged in a single package.Inside it is also a pull-up resistor.In such a model similar conclusions as that of the bipolar.It is not difficult to guess that the multimeter to check the transistor component can be exactly the same as BT.It should be noted that some types of digital multimeters test mode have minimal voltage at the terminals of 1.2 V, which is insufficient to open the p-n junction, in which case the device showing the gap in the chain.

Figure 5 - Diagram of the Darlington

If, after reading this article you still do not fully understand how to check transistor multimeter video tutorial below will clearly see the scan technology:

Thus, the task of verification of the circuit element is reduced to a sequence of "proring» p-n junctions, and if they are correct, the device can be regarded as a worker.We hope that you now know how to check transistor multimeter at home!

Advised to read:

• Inspection Procedure RCD
• How to check the correct operation of the meter
• How to identify a short circuit in the network