wn4isx wrote:
I can't see a B/E junction going into avalanche mode.
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Why not?
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Whether you call it "avalanche mode" or "zener mode", for most of us engineers that is less important than the fact that it breaks down due to reverse voltage across the junction.? Almost all modern BJTs have a base-emitter breakdown voltage that is rather low, about 5 V.? (Whereas the breakdown voltage of the base-collector voltage is generally considerably higher and it varies over a wide range, and depends on its part number.)
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I am not certain but I'm pretty sure that is what the circuit dues, in the original poster's message.? Base-Emitter breakdown.? Not base-collector.
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(Technically, "avalanche mode" breakdown refers to reverse breakdown that is greater than about 5 V or so.? At the physics level, they are rather different mechanisms, but the transition from zener mode to avalanche mode is gradual and there is a range where they overlap.)
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Andy
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