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Tri-state buffer with bipolar npn transistors

A project log for Multiplexed 7-segment display

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pavelPavel 05/02/2017 at 05:090 Comments

After some tinkering, trial and error with breadboard, I arrived at seemengly good schematics for the t-buffer, using 5 npn bjts and two resistors. This turns out to be invertor with active-low enable, so it have to have inverted input. I figure, for saving slightly on components, I will use it as is, and connect its input to inverted out of flip-flop or latch.

This variant's HIGH output is one diode drop lower than positive rail, but I think, it will be acceptable for driving my dtl gates.

Here is the schematics with measured voltages in table:

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