## Measuring gain and leakage in germanium transistors

Putting two effects in one box almost looks too easy, but you will save a lot of time reading the frequent questions before starting such a project...

### Measuring gain and leakage in germanium transistors

I recieved this from a helpful gentleman named Димитър Димитров ---- Measuring of germanium transistors with digital multi-meter may be very inaccurate due to several reasons. Our engineer Mr. Plamen Vasev (dpebay@abv.bg) has invented a new method to check quality of germanium transistors via two measurements of the base current. With this we calculate the gain and also can conclude for what the measured transistor can be best used. 1. The leakage current Icbo is measured first. 2. Then the base current Ib is measured at fixed collector current Ic (eg. at 0.5 mA, fixed by a resistor connected to the emitter). 3. Finally the gain hfe = Ic/(Ib+Ibco) is calculated. Example: If Ibco=4µA, Ic=1000µA, Ib=12µA, then hfe=62.5 If this example transistor was measured with a digital multi-meter it would show a figure about 100!! or about 60% error!!!???

Best Regards,Dr. Dimiter Dimitrov Manager BgEbus Is this method different than the one you longtime EE typed have been using?
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noelgrassy
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Darn thing must have thought my fluent use of Cyrillic was some kinda "cussin'". Well, it's merely a gentleman's appellation. Pussy fucking software shit. Thankyou for reading anyway, NG
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noelgrassy
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### Re: New method of measuring germanium transistors?

noelgrassy wrote: Measuring of germanium transistors with digital multi-meter may be very inaccurate due to several reasons. Our engineer Mr. Plamen Vasev (dpebay@abv.bg) has invented a new method to check quality of germanium transistors via two measurements of the base current.

Mr. Vasev is a little late.

See "The Technology of the Fuzz Face" from 1998 at GEO http://geofex.com/Article_Folders/fuzzface/fffram.htm. It wasn't new when I wrote it up, as the early testers back in the 60's did this as well.
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Here's the circuit that's used for testing 'em AC128's

Could this be adapted to NPN silicon transistors as well?

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Stuggi wrote:Here's the circuit that's used for testing 'em AC128's

Could this be adapted to NPN silicon transistors as well?

Yeah, it could - except the leakage number is useless. Silicon has well over a thousand times less leakage than germanium (or should!) so any silicon that shows any "leakage gain" at all should be tossed in the rubbish bin.
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Will the circuit work as it is with a NPN or do I have to reverse the power source?

Stuggi

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### Re:

Stuggi wrote:Will the circuit work as it is with a NPN or do I have to reverse the power source?

Yes, inquiring minds want to know. Logic would dictate so, but I'm not versed well enough in Electronics or logic. Hell, I'd be happy to rent some common sense once in a while. Anyway, we'll leave a light on for yez if you wanna revisit this thread.
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