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Problem with output logic levels

A project log for Simple counter/clock

4-bit counter hooked up to 7-segment display showing succession of hexadecimal digits

pavelPavel 04/14/2017 at 04:510 Comments

For decoder I used simplest diode 4AND logic gates (image), assuming they would work properly, and give +Vcc for high and 0.6V for low.

Unfortunately, output for HIGH is measly 1.6-1.7V and it is too low for driving display unit.

I am still cannot understand, why is it so.

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