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Old 30th September 2003, 10:58 PM   #1
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Default Transistor leakage?

Over the weekend I threw together an amp. It used four transistors per side. I wanted a lot of gain so I could cut it back with NFB so I used a triple darlington arrangment with the emitter on the rail and fed its base with a grounded transistor. The problem was that the output is so sensitive, that the grounded transistor starts conducting forward at 0.2v enough to put a lot of current through the speaker. I fixed this in a way by grounding its collector through a resistor so now it conducts forward at 0.4v instead. It is a power transistor so I was wondering if there's anything that I can use that will turn on sharply at 0.6v because that's what I need. The leakage at 0.2v is actually killing my gain because I have to have the bias turned back so much. I know the gain is definately there on the second stage because when I touch it's base I get a huge peak-to-peak 60hz hum on the output. Would a tiny signal transistor switch cleaner?
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Old 1st October 2003, 08:48 AM   #2
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Can you post some sketch over the schematics?

A "Tripleton" containing just three transistors is not a very good idea. You must have some resistors also between the base and emitter.
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