not gate

[Screech]

I'm after a not gate.
I can't find them.
Are they actually called a not gate?
thanks.

 

[DigiTan]

They usually go by the name "inverter" if it's an embedded device. The 74X05 Hex Inverter is still in production. Were you looking for a TTL or CMOS device?

 

[Screech]

DigiTan,
ttl or cmos? I don't know the diffrence.

but I nead it to think that an "ON input" is an input that has been grounded.
and an "off input" is an input that has not been ground.

hope you understand.

 

[DigiTan]

The CMOS versions seem to be considered out-of-date, so I guess you're looking for TTL in general. All generic inverters like the 74LS04 or 74LS05 will work in the classic NOT gate fashion. Major manufacturers will have thousands of these in stock, so they are very cheap and ship easily.

* Heres a Texas Instruments site on a popular Hex Inverter.

[edit]Oh, yeah. "TTL" and "CMOS" just refer to the chip's composition, and its input and output voltages. A TTL device will read voltages in the range of 0-0.8volts as a zero, and voltages of 2-5volts as a one. CMOS allows for higher voltages.

 

[Screech]

DigiTan, I went to that link, and it says:

These devices contain six independent inverters. To perform correctly, the open-collector outputs require pullup resistors. These devices may be connected to other open-collector outputs to implement active-low wired-OR or active-high wire-AND functions. Open-collector devices often are used to generate high VOH levels.



Now, I don't understand all this terminology,
but i still nead to know wich inverter can function with:

An "ON input" is an input that has been grounded with a resistor.(similar to the base pin of a pnp transistor)
An "off input" is an input that has not been grounded.

thanks DigiTan
.

 

[DigiTan]

No problem. All this is saying is that the six NOT gates are independent--or "seperate" from each other. The second part means that you'll need pull-up resistors (or pull-down, if you want) to keep the input from floating randomly if nothing else is connected to it. The last 2 sentences aren't too important for now.

Here's a cutaway drawing:
**broken link removed**
...Here, if you only wanted to use 1 NOT gate, you could use pin 1 as the input and pin 2 as the output. (It doesn't have to be pins 1 and 2, we could just as easily use 3 and 4, 5 and 6, 8 and 9, etc.). This way, the logic level at pin 2 will always be the opposite of pin 1.

The other 5 NOT gates can be used in the same manner; or can ignore them (remember they're independent).

 

[DigiTan]

Also, a single NOT gate can be made from a bipolar transistor is this fashion...
**broken link removed**

 

[Screech]

got it, Digitan.
thanks for the gif.