Both PNP and NPN transistors can be checked using this circuit. Here is a very simple circuit that can be used to check the hfe of transistors. The voltage source is a 6V power supply which is. In this post we learn how to make a simple yet efficient transistor/diode tester circuit, that will not only test the quality of a BJT, but will also help to identify whether it is is an NPN or a PNP. Simple Transistor Tester (Contains both Circuit Diagram and PCB Lay Out) 3. If you have no moving coil instrument available, it is of course also possible to replace M1 with a digital meter. This is a very simple transistor tester circuit the circuit can be used to test NPN and PNP transistors. The purpose of S1 is to reverse the polarity: the upper position drawn is for NPN transistors, the bottom for PNP types. It will be clear that position 2 of S3 is intended for high gains of up to 1000 and position 3 for gains of 0 to 100. In position 3 the base resistor is 10 times lower (R1 = 56 kΩ), so in this case, the reading has to be multiplied by 10 to obtain the gain. Therefore, the value indicated by the meter, when S3 is in position 2, has to be multiplied by a factor of 100 to obtain the gain of the transistor. If the transistor has a gain of 1000 it will cause a collector current (and therefore a metered current) of 10 mA, causing full-scale deflection of the moving coil instrument. This tutorial is split into a series of sections, covering: Symbols, Pins, and Construction - Explaining the differences between the transistors three pins. It can be easily accumulated on a general purpose PCB. Its circuit is simple as compared to other transistor testers which is useful for both technicians and students. Once pointed, the red LED can then identify the PNP transistor base. Transistor Tester Circuit Diagram By Ashutosh Bhatt This project is a transistor analyzer, suitable for testing both NPN and PNP transistors. The voltage of a healthy transistor should be 0.7V, and the measurement across the emitter collector should read 0.0V. Connect the red (positive) lead to the base terminal of the PNP transistor, and the black (negative) lead to the emitter or base terminal of the transistor. With S3 in position 2 this will be (6 V – 0.6 V)/560 kΩ = approx. Test Process: Position the transistor to the three circuit terminals of Circuit 1 (located either below of left of the terminal). The digital multimeter consists of two leads: black and red. When a transistor is being tested (S2 open, S3 in position 2 or 3) a current will flow through the base-emitter junction of the transistor under test, the value of which can be computed by dividing the voltage across R1 or R2 by its resistance.
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