☑ Germanium Transistor Leakage Current

Silicon is actually preferred to germanium within the manufacture of semiconductor devices due to the following reasons. After years of experimentation and listening it is agreed that the best match uses a low gain in the first stage hfe80 approx and a high gain in the second stage hfe120 approx.

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Germanium transistors tend to have high leakage current and an inconsistent gain value hfe.

Germanium transistor leakage current. They just put a metered amount of base current in and look for how much collector current comes out. Current leakage of over 10 micro amps can be a method of determining that a transistor is built on a base of germanium instead of silicon. Compared to silicon germanium is a rare and expensive metal to mine.

These are fine outgrowths of the crystalline structure known as whiskers that over time can short out a circuit. Also simple transistor testers such as those found on multimeters cannot tell the difference between collector current and leakage current so they show transistors with high leakage as having high gain. There is an excellent article the technology of the fuzz face by rg.

Keen that inspired me to try out a germanium fuzz build. On the small bear fuzzface faq there is a drawing that illustrates how to measure transistor leakage near the end of the page. All the nos npn germanium i have seen leak like a sieve.

Silicon is cheap and abundant in silicon leakage current is less affected. However all modern dmms assume that the transistor being testing has no leakage at all. Heres how to separate the wheat from the chaff.

In the article rg. The germanium transistor has a collector base leakageicbowhich is amplified twice and cause the led to turn on even when the base of the germanium doesnt get signal. Leakage current completely screws up the dc bias of circuits like the fuzz face.

This is a circuitsziklai pairthat amplified a small current by a germanium and silicon transistor in order to turn on a led. Includes the schematic for a testing rig and lays out a formula to calculate leakage and actual gain of germanium transistors. Testing ac128 transistors for leakage and gain september 30 2011 audioradio electronics effects pedals diy 2 comments now that i have a test rig set up i can start to measure some transistors.

With germaniums inherently higher leakage this just makes a leaky device look like a higher gain device. The ac128 is a great sounding germanium transistor but if you buy many of them there will be a large number left over that have too much base to emitter leakage to be useful in a voltage amplifier circuit.