QnDhfe - the Quick & Dirty transitor Hfe tester - diyAudio
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Old 30th January 2016, 10:47 AM   #1
nnx is offline nnx
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Default QnDhfe - the Quick & Dirty transitor Hfe tester

Hello,

In search for an ultra-simple hfe-meter I found this on the EEVblog:

How come transistor beta hFE test is only on cheap DMMs? - Page 1

After simulating in spice and adjusting the resistor values a bit, I decided to give it a go - dead pcb style. Materials are a 3V battery w/holder, 5 resistors, one 8-pin ic-socket and some random piece of leftover board. It seems to work but accuracy is no good, but it makes it possible to select and match transistors.

Please enjoy
nnx
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Old 30th January 2016, 11:05 AM   #2
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Q2 is drawn wrong, upside down!
Answer to your question is because if you purchase a quality DVM, one requires all the cost to be for a DVM. One can purchase a transistor tester separately and very cheaply.
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Old 30th January 2016, 11:26 AM   #3
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Default Corrected!

Thank you for the comment! Q2 was upside down, but has now been rotated in the schematics. The output from the tester is in millivolts, one mV approximates one "degree" of hfe.

Of course it would be better with a proper dvm with built-in tester, or a dedicated transistor tester. But this is just a little fun project.....
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Old 30th January 2016, 01:21 PM   #4
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And very useful too.
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Old 30th January 2016, 04:30 PM   #5
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Quote:
Originally Posted by JonSnell Electronic View Post
Q2 is drawn wrong, upside down!
Answer to your question is because if you purchase a quality DVM, one requires all the cost to be for a DVM. One can purchase a transistor tester separately and very cheaply.
There is also the safety aspect. A transistor tester on a DMM pretty much always exposes the voltages on the inputs on the transistor tester pins as well. This is both a risk for arc over a well as shock/electrocution of someone who might have their hands near the pins. Combine this with the fact that the transistor tester in these devices gives you a very relative value and it just becomes too many negatives to include in a quality meter.
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