I have a bunch of Darlington NPN Transistors TIP142 that are removed from two separate identical boards. The 1st one have the TO−218 CASE (left side of the image) and the 2nd the TO−247 CASE (right side of the image)


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With the Diode Test when I measure the Base-Emiter with N-Probe to Base and P-Probe to Emmiter with the TO−247 I get about 1.368V for all of them, but the same measurement for the TO−218 is OL for all of them (Please note that the multimeter with no probes connected is also indicate OL).

The resistance between them is for the TO−247 about 3.56KOhm and for the TO−218 about 15KOhm.

The other measurements seems to be identical.

So I am really confused and I wonder if some of them are faulty.

Edit: In my opinion since there are two resistors in series between Base and Emitter there should be a voltage drop. In the TO-247 case my multimeters show OL maybe because there is no much current to draw to show any measurements. Note that the resistance in that case is about ~15KOhm instead of the 3.56Kohm of the TO-247. The datasheet referes that the 1st resistor is ~8K but for the 2nd just ~40 ???? what ?

Multimeter with probes not connected indication

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    \$\begingroup\$ please take a clear image of TO-247 and upload it in question.. \$\endgroup\$ – Satish Singupuram Jan 10 at 20:17
  • \$\begingroup\$ The resistance measurements seem to indicate that the TO-218 versions have a higher base-emitter voltage -- are you sure you were reading zero, or was your meter out of range? Do you know what the diode voltage measurement range is on your meter? \$\endgroup\$ – TimWescott Jan 10 at 21:07
  • \$\begingroup\$ Measure the resistances in both directions (polarities) to see the effects of the base-emitter junctions. \$\endgroup\$ – AnalogKid Jan 10 at 22:12
  • \$\begingroup\$ @AnalogKid It does not matter. Its always the same. \$\endgroup\$ – Maverick Jan 11 at 7:13
  • \$\begingroup\$ @TimWescott the indication I get is .OL which is the same i get when is not connected (stand by). \$\endgroup\$ – Maverick Jan 11 at 7:14

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