Hello everyone,

I just started messing around with circuits, so I got a 555 timer and hooked it up.

But when I was reading the datasheet I noticed that the not gates get two inputs. I'm not very experienced with circuits, but I could have sworn that not gates only get one input.

I also noticed that they have plus and minus signs, but that just added more confusion.

I've made an attachment of the pdf.(Its on the second page, first diagram)

Thanks

 

A 555 is an open ended circuit. The NOT function (aka Inverter) is just one of them, and it has to be wired to make one.

I cover that in this article.

.

 

Actually they aren't not gates.

They are level comparators.

The positive input for each comparator is tied to a value related to the chip supply voltage.

In the case of the trigger comparator it's 1/3 Vcc. In the case of the threshold it's normally 2/3 Vcc for most purposes, but this can be overridden to some extent by a control input. These 1/3 Vcc and 2/3 Vcc values are set up by the three 5K resistors in series from Vcc to supply common.

 

Oh, I get it, that fixed a bunch of my problems!

Thanks