0000 0000 0001 1011

CD4069 CMOS Hex Inverter

What to do when your signal comes out reversed from what you need? If it is only one problem signal, then you could whip up a transistor-based solution as per this useful website. If you need seven signals inverted because of an ordering mishap, then a hex inverter (plus a single transistor solution) might be a better approach.

An inverter is a common logic gate (NOT gate) which has the following symbol and truth table.

If you clump a few NOT gates together in a logic chip - you get a CD4069 hex inverter (see screenshot from the datasheet below). So a "1" or "HIGH" sent to pin 1 (A) returns a "0" or "LOW" on pin 2 (G=Ā), and vice versa.

Fortunately in the many buckets of bits I have a few CD4069UBE chips lying around looking for a purpose. The pinout is very straight forward, but before I use the whole chip to reverse a bunch of signals (next blog), I will test it on a very simple circuit - involving of course a blinking LED.

The 555 is not really disembodied out to the side, but it is just shown here providing a clock signal which is a "1, 0" square wave at a particular frequency. And to show that all of the inputs/outputs are ready for quality inverting, I've plugged all six in plus an extra transistor NOT gate - but why seven? Well, next time I'll look at "fixing" a seven segment display gone slight awry.