Real-Life NOT Gate: How Does It Work?

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In summary, a NOT gate, also known as an inverter, turns a logic level of 1 into a logic 0 and vice versa. It is commonly used to convert signals from one logic level to another and can also be used to sharpen signals. In a genuine circuit, a NOT gate is typically the smallest and fastest gate, making it ideal for use as a buffer. In a calculator, a NOT gate is often implemented using two MOS transistors, with one transistor opening to produce a high signal and the other opening to produce a low signal. A write only memory is a joke concept where you can only write information to it but cannot read it back, and it is commonly used as a marketing gimmick. Overall, NOT gates
  • #1
Nexor
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How does a NOT gate works in a genuine circuit? Like in a calculator?

Thanks in advance,

Nexor.
 
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  • #2
A NOT gate turns a logic level of 1 into a logic 0, and vice versa. This can be used when a circuit that operates by receiving a logic 0 has need to be operated by a logic 1, for example. A NOT gate is typically the smallest and fastest gate, because with semiconductor circuits it requires the fewest components, so it can also be used as a buffer, and to sharpen signals that are not as digitally clean as some circuits need. A clean digital signal should be logic 0 or logic 1, and not waver around somewhere in between.
 
  • #3
But how would it work? I mean, a line powered with 1V with a inverter (or NOT gate) in it's path would turn the signal to it's opposite value, which might be 0V, am I right? But how this same inverter would turn 0V into 1V?
 
  • #4
Nexor said:
But how would it work? I mean, a line powered with 1V with a inverter (or NOT gate) in it's path would turn the signal to it's opposite value, which might be 0V, am I right? But how this same inverter would turn 0V into 1V?
Consider a single transistor in common-emitter configuration. When you put high on the base, transistor opens and pulls down voltage on the collector to 0. When you put low on the base, the resistor between collector and vcc pulls the voltage up to vcc.
The real world circuit in a calculator probably uses two MOS transistors:
http://www.allaboutcircuits.com/vol_4/chpt_3/7.html
where the low signal opens the top transistor and results in high signal on output, and high signal opens the bottom transistor and results in low signal on the output (during transition, very briefly, both transistors are open)
 
  • #5
Dmytry said:
Consider a single transistor in common-emitter configuration. When you put high on the base, transistor opens and pulls down voltage on the collector to 0. When you put low on the base, the resistor between collector and vcc pulls the voltage up to vcc.
The real world circuit in a calculator probably uses two MOS transistors:
http://www.allaboutcircuits.com/vol_4/chpt_3/7.html
where the low signal opens the top transistor and results in high signal on output, and high signal opens the bottom transistor and results in low signal on the output (during transition, very briefly, both transistors are open)

Ohh I think I got it... It's definitely not how I expected though... Thanks :)
 
  • #6
Now that you have your answer, I have two more for you!

1) What is a none gate?....A gate that can accept all logic levels, no propagation delay, when you put in a 1, you get 0, if you put in a 0, you get 0.!

2) What is a WOR...Write Only RAM?!......A RAM that have infinite storage locations, you can use any logic levels, you can write as fast as possible.

And yes, I invented these two!

Is this out of line even for Christmas Eve?:rofl: :rofl: :rofl:
My big party is tomorrow, I just spent the whole day cooking and setting up the place. Getting a little wacky even with no alcohol!

Merry Christmas

Alan
 
  • #7
i remember the "write only memory" well - signetics i think.
only IC ever with pins for filament voltage, note 6.
definitely from our era...

http://www.national.com/rap/files/datasheet.pdf [Broken]

http://www.national.com/rap/Story/WOMorigin.html [Broken]
merry christmas to all,,

old jim
 
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  • #8
I did not know that, that was before my time!
 
  • #9
yungman said:
Now that you have your answer, I have two more for you!

1) What is a none gate?....A gate that can accept all logic levels, no propagation delay, when you put in a 1, you get 0, if you put in a 0, you get 0.!

2) What is a WOR...Write Only RAM?!......A RAM that have infinite storage locations, you can use any logic levels, you can write as fast as possible.

And yes, I invented these two!

Is this out of line even for Christmas Eve?:rofl: :rofl: :rofl:
My big party is tomorrow, I just spent the whole day cooking and setting up the place. Getting a little wacky even with no alcohol!

Merry Christmas

Alan
1) I think you are referring to the false gate, which will output 0 (false) no matter the input.
2) Whaaat??
 
  • #10
yungman said:
I did not know that, that was before my time!

Oh yeah... The old times...
 
  • #11
Nexor said:
1) I think you are referring to the false gate, which will output 0 (false) no matter the input.
2) Whaaat??

Then call it your invention!

Merry Christmas.
 
  • #12
yungman said:
Then call it your invention!

Merry Christmas.

Noo hahaha, I just said I didn't understand the second question and that the first one might be the false gate.

Merry Christmas to u too :D
 
  • #13
You mean the write only memory? As Jim called it WOM, you can write anything in, but can never read it back!
 
  • #14
yungman said:
You mean the write only memory? As Jim called it WOM, you can write anything in, but can never read it back!

How would it work? Plus, how can it be used?
 
  • #15
Nexor said:
How would it work? Plus, how can it be used?

Merry Christmas! We are all joking!
 
  • #16
Nexor said:
How would it work? Plus, how can it be used?

That's a joke. It's when you have nothing connected to the memory bus. You can do writes, but you can't read anything out. A pun on the read-only memory which can only be read but not written, the write-only memory can only be written to, but not read. Sometimes external devices function as 'write only' memory - e.g. you can connect the LED here and make it blink when you write 1 to this address. It is actually common to treat output operations as memory writes, many CPUs lack any specialized output ports.
 
  • #17
As the article linked says, Signetics placed that WOM datasheet in the April issue of a design magazine as an April Fool's joke, for marketing goodwill. I was a young engineer at the time and it sure appealed to me...

to original poster - google "7404 hex inverter", better yet buy one and experiment...
 
  • #18
The software implementation of write-only memory was invented by programmers long ago.

On VMS it was a device called NLA0:

Any write to this device succeeded immediately. It always read a null string or EOF depending on the mode it was opened with.
 
  • #19
ahhh DEC gear? A programmers dream.

i detest those Intel swapped nibbles.
 
  • #20
You all can't do that with me, I'm just a newbie! XD
 
  • #21
Nexor said:
You all can't do that with me, I'm just a newbie! XD

We don't mean to confuse you. I thought you have your question answered already before I even came in for some Christmas joke! This post just took on a new life from that onward and has nothing to do with you, just a few old timers' joke!
 
  • #22
yungman said:
We don't mean to confuse you. I thought you have your question answered already before I even came in for some Christmas joke! This post just took on a new life from that onward and has nothing to do with you, just a few old timers' joke!

Okidoki :D
 

1. What is a NOT gate?

A NOT gate, also known as an inverter, is a logic gate that produces an output value that is the opposite of its input value. It is represented by the symbol "¬" or "NOT".

2. How does a NOT gate work?

A NOT gate has only one input and one output. The output is the inverse of the input, so if the input is 0, the output is 1 and vice versa. This is achieved through the use of transistors and their ability to switch between on and off states.

3. What are the applications of a NOT gate?

NOT gates are commonly used in digital circuits to invert signals, which can be useful in controlling the flow of data. They are also used in combination with other logic gates to create more complex circuits and perform logical operations.

4. Can a NOT gate have more than one input?

No, a NOT gate can only have one input. However, multiple NOT gates can be connected together to achieve the desired input and output combinations.

5. What is the truth table for a NOT gate?

The truth table for a NOT gate has two rows and two columns. The input is listed in the first column and the output is listed in the second column. The output is always the opposite of the input, so the truth table for a NOT gate is:

Input (A) Output (¬A)
0 1
1 0

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