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Vintage threads from the first ten years

Beta dc

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5/15/1999 7:07 PM
Stan Bailey	Beta dc I'm begining not to trust my meter for measuring transistor gains. I'm wandering if I were to actually breadboard a circuit like say a Fuzz Face, then measure the Base and colector current to establish Hfe. From what I learned in class Bdc= Ic/Ib. Wouldn't this give me the most accurate reading for that particular circuit? Any info will be appreciated. Thanks in advance, Stan

5/16/1999 6:17 AM

Measuring Hfe

Yes, measuring gain in the actual circuit conditions will give the most accurate result for those conditions.

The catch is the phrase "for those conditions".

Transistor current gain is anything except constant. It varies with temperature, current level, collector-base voltage, and probably the phase of the moon. In DMM's you get falsely high readings of transistors because any leakage appears to the meter to be additional current in the collector.

This is one of those things where you have to not try too hard. Use the meter reading as an indication, not the gospel truth.

5/16/1999 1:34 PM
Stan Bailey	Thanks for filling in the Gaps R.G.! Now, I better start measuring, there is a full moon a comin'. Stan

5/16/1999 2:38 PM
R.G.	I hear the gains get more better (whichever direction that is) if you measure them at midnight at a crossroads...

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