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Logic gate output won't go low enough to turn off NPN transistor

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Benta:
Apologies: forgot to mention that the Schottky/Baker clamp diode is a BAT41. Corrected in my reply.

Benta:
Try this instead. Let's call it "active turnoff". You really need to get hold of some small-signal Schottky diodes.
Turn on is now ballpark, a 2N2222A which is specified for switching is appr. 2x faster.

Trace colours the same as in previous post.

Benta:
Without the Baker clamp (D1 removed):

bdunham7:

--- Quote from: Kleinstein on June 09, 2023, 08:29:55 pm ---The baker clamp does not really work with a "normal" diode.

--- End quote ---

The two-diode one works to keep the collector from going below the base with any sort of diodes as long as they both have the same Vf.  The three-diode version which goes beyond the 'clamp' action adds a diode to drain the charge from the base back through the input signal, bypassing all or part of the input resistor.  The input signal has to actually go low (not open) and be able to sink this current.  Using a Schottky for this third diode probably makes sense, but here's an interesting example using regular 1N4148 diodes. 

https://hackaday.io/project/18138-bullet-movies/log/49133-faillog-first-flash-driver-prototype

Benta:

--- Quote from: bdunham7 on June 10, 2023, 12:07:12 am ---but here's an interesting example using regular 1N4148 diodes. 

https://hackaday.io/project/18138-bullet-movies/log/49133-faillog-first-flash-driver-prototype

--- End quote ---
Sorry, but whacking a transistor base through 100 ohms is easy for anyone. Especially at only 500 kHz. Not impressed.
But OK, that's hackaday I guess. I don't go there.

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