If the positive lead of a DMM, with the mode set to ohmmeter is connected to the base and the negative lead to the emitter and a low resistance reading is obtained, then what is the type of transistor that is being tested?a)NPNb)PNPc)Faulty transistord)Not a transistor, it is a FETCorrect answer is option 'A'. Can you explain this answer?

Question

Answer

Answer:

Explanation:

When testing a transistor using a Digital Multimeter (DMM) set to the ohmmeter mode, the positive lead is typically connected to the base and the negative lead to the emitter. This configuration allows the DMM to measure the resistance between the base and emitter junction of the transistor.

If a low resistance reading is obtained in this configuration, it indicates that the base-emitter junction is forward biased, which means that the transistor is functioning as an NPN transistor. In an NPN transistor, the base-emitter junction is forward biased when the base is positive with respect to the emitter.

Here's a detailed explanation of why the low resistance reading indicates an NPN transistor:

- NPN Transistor: In an NPN transistor, the base-emitter junction is formed between a p-type material (base) and an n-type material (emitter). When a positive voltage is applied to the base with respect to the emitter, it creates a forward bias across the base-emitter junction. This allows current to flow from the base to the emitter, and the transistor enters its active region of operation.

- Forward Bias: When the base-emitter junction is forward biased, it allows current to flow freely from the base to the emitter. This results in a low resistance reading when measured by the DMM in the ohmmeter mode. The low resistance indicates that the junction is allowing current to pass through, which is characteristic of an NPN transistor.

- PNP Transistor: In contrast, if the DMM were connected in the same way (positive lead to base, negative lead to emitter) and a high resistance reading was obtained, it would indicate a PNP transistor. In a PNP transistor, the base-emitter junction is forward biased when the base is negative with respect to the emitter.

- Faulty Transistor: It is also possible that a faulty transistor could result in a low resistance reading. However, without further information or testing, it cannot be conclusively determined if the low resistance reading is due to a faulty transistor or if it is indeed an NPN transistor.

Therefore, based on the given information, the type of transistor being tested is most likely an NPN transistor (option A).

Answer

There are multiple ways to test the BJT to be npn or pnp using a DMM based upon which terminals are connected to which lead of the DMM. If positive is to base and negative to the emitter of the BJT, and if a low reading is obtained and not a over limit, then the transistor is NPN.

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