Transistor tester. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Transistor tester, measure hfe. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Measuring technology

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This simple diagram will help determine current transfer coefficient of the transistor npn structure. The scheme, so to speak, is the basis that can be turned into something more.

Let's go over the details. The transistor 2SC1740 (NPN) was chosen as the test subject, in its place we put the one that needs to be measured (TRx). Transistor T2 is in key mode, I took 2SA933 (PNP). LED any at your discretion.

Transistor tester, measure hfe

The first version of the circuit Fig. 1 on variable resistors, these are R5 and R4. You can leave one (R5). Their denomination is as large as possible, say 1 Megaohm (Mohm). Range >1700. Or do it differently, put R5 at 1 Mohm, and R4 say 500 kOhm, this will give more accurate readings. Variable resistors are connected in the usual way, and not according to the potentiometer circuit, which gives the conversion of voltage U into current I.

We feed all this from 9V, it is possible from the "crown" battery. Reducing power will have a bad effect on the readings.

This device is made on a printed circuit board. Or in the body. Resistors R5 R4 will need to be calibrated; this can be done in different ways, you can measure the resistance with a tester or multimeter and sign the values. Example: We connect the probes to the resistors, turn the resistor to 82 kOhm and mark 100, 168 kOhm - 200, etc. look at the tables.

Transistor tester, measure hfe

The second version of the circuit on fixed resistors. Everything is the same here, first we insert the one that needs to be checked instead of the 2SC1740 transistor, then we connect the resistors to the base of the transistor in turn, you can use the closing buttons, in the printed circuit board that I gave, there are jumpers like - Jack, although this is not very convenient, but it takes up less space.

Starting from 100 and up to 500, if the transistor has a coefficient of ~ 300, then the LED will light up when S3 is pressed.

If you need to measure a coefficient of more than 500, then you just need to add resistors, we take the ratings in the tables.

Transistor tester, measure hfe

Here is a version of the circuit up to 900, as you can see, it turns out to be very cumbersome, and the board will also turn out to be large, so it’s easier to do it on variable resistors according to fig. one.

The table looks like this:

100 - 84,1 kOhm
200 - 168,3 kOhm
300 - 251,5 kOhm
400 - 335,5 kOhm
500 - 418,7 kOhm
600 - 503 kOhm
700 - 575 kOhm
800 - 656 kOhm
900 - 737,5 kOhm
1000 - 820 kOhm
1100 - 901 kOhm
1200 - 983 kOhm
1300 - 1065 kOhm
1700 - 1392 kOhm

As an idea, you can try to put a thyristor in the T2 collector so the LED will light up more accurately. I haven't tried it myself. I don't have a thyristor on hand.

I think there will be no problems with PCB layout, but just in case, I post them in the LAY format for the Sprint-Layout 5.0 program. And schemes for the sPlan 6.0 program. Download 30 kb.

Publication: cxem.net

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