How to use Arduino to Identify a Transistor and a MOSFET?

I saw some Multi function Tester can Identify Transistor and MOSFET, can I get clue how to code it?

Tester Link:


This is just one of MANY variations all over the web.

I believe this was the original but am likely wrong on that count, there are so many variations it is hard to know (original in German):

Follow up: I see that Banggood is no longer about low prices. You can find the some item on eBay for half the price. Shop carefully. There is a very long thread on building your own (with links to software) over on the EEVBLOG.

Hi @shanren
Testing a MOSFET is different from identifying a MOSFET.
Testing is possible with a good project, but identifying I find it almost impossible.

RV Mineirin

Thank you.
I'll read.

Thank you.
Actually what I like to know is how the tester distinguish that two when do the test.

Theoretically it's not very difficult. The main difference is:

  • The base of the transistor draws current. It has Vbe as a diode (< 1V).
  • The MOSFET gate practically does not consume current. Vgs is equal to the Vin.

However, you need a very sensitive current detector because some transistors (especially Darlington transistor) can have very small base current values. The Vbe of a Darlington transistor is twice that of a bipolar one.
There is also Sziklai Transistor and some others.

You might have a look @Grumpy_Mike 's transistor tester

I'll read it.
here attaches the picture
how that tester Distinguished the Transistor and MOSFET and shown that.

I am finding Aliexpress generally better than eBay. :roll_eyes:

From my experience AliExpress has seller protection while eBay has buyer protection. AliExpress is slightly cheaper and has much wider supply but DOA chips are more common. What is worse any complain is rejected because they want a "proof".

In a MOSFET the gate is completely isolated from the other terminals (at DC).

A BJT looks like two back-to-back diodes.

To identify a MOSFET you'd first rule out a BJT, then look for one pin that
appears to float to whatever test voltage you apply to it though a resistor.

Then you'd start investigating the rest of the pinout and polarity, then try to
measure transconductance...

All a tester does is automate how you'd check an unknown component by hand -
try out various conjectures in all possible permutations of pinout.

I used to use Aliexpress.

Aliexpress is OK. I never met a complain be rejected, they want a 'proof', yes, but just pictures to show them whatever the situation is.

I'll try that.

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