AND gate output

And-gates are digital gates, so you can't input analog signal to them. In digital system, there are just a low-level, which is usually 0V, and a high-level, which is some voltage depending on the system. So you must know what is the high level voltage in your and-gate. If it's a basic TTL-chip, it's 5V. So you can't input any other amplitudes than

0V or 5V.

If both of its inputs are low (=have 0V on them), the output will be low (0V)

If one of its inputs is low (0V) and the other is high (5V), the output will be low (0V)

If both of its inputs are high (5V) then the output will be high (5V).

That's why is it AND-gate, as the input 1 AND input 2 must both be high to get the output going high.

Thanks a lot simoc for your valuable response.But if 4.8V and 5V are given as inputs then what would be the output? 4.8V is also considered as High.Right?

Simoc wrote:

While the voltage may vary by a few tenths of a volt or so, digital logic only has two states (well if you concider an undefined state 3 ) high and low. Anything from about 0 to .8 is a low and from 2 to 5 is a high. The area between about .8 and 2 is undefined and should not be in a digital circuit . All the above should be for a 5 volt TTL circuit. Other voltages and types of ICs will be similar in the way they work.

After all that, if you have an input gate with many inputs and they are all high or low, the output will still be almost the same voltage, either the normal high or low.

You need to look at the specs for a particular logic standard. Are you asking about:

TTL LVTTL

4000 family CMOS LVCMOS 3.3V LVCMOS 2.5V SSTL 2.5V SSTL 1.8V HSTL 1.8V HSTL 1.5V LVDS BLVDS LDT LVPECL PECL ECL GTL ... which one???

Each standard will state, for inputs and outputs (a separate set of values for each) -- max voltage for a '0' min voltage for a '1' along with many other characteristics.

Since you mentioned 4.8V and 5V, I'm assuming you're talking about TTL. For TTL (commercial grade), an input sees a '0' if the voltage is less than

0.8V, and sees a '1' if the voltage is higher than 2.0V. Outputs (for a given max load) will put out max of 0.4V for a '0', and minimum of 2.4V for a '1'.

Don't be afraid to open some datasheets. There is really no other way to learn the specifics

Bob

--- Please bottom post.

Bob already gave you the answer, (shown below) and it's that the output voltage for a TTL "high" can be anywhere between 2.4V and 5V for a supply voltage of 5V.

-- John Fields Professional Circuit Designer

Please bottom-post, like mentioned, meaning that put your reply _below_ the quote, NOT ABOVE.

But then the answer :-) It's usually nearly the operating voltage which you input to the Vcc-pin of the chip. And it should be something about

5V, within the limits of its tolerance (I don't remember, see the datasheet, although the 4.8V will be within the tolerance).

But actually it doesn't probably matter anyhow, as probably nothing that will be fed by its output will "care" about such low (0.2V) diference.

On 7 Jul 2006 04:09:47 -0700, in message , "novice" scribed:

You are trying to drink whiskey from a bottle of wine. Analog circuits deal with magnitudes, digital circuits deal with states. The magnitude of the output of an analog circuit is dependent upon the magnitudes of the inputs. The state of the output of a digital circuit is dependent upon the states of the inputs. There is no direct relationship between the magnitudes of the inputs of a digital circuit and the magnitude of its output.

--

If life seems jolly rotten, there\'s something you\'ve forgotten,
and that\'s to laugh and smile and dance and sing!

--
You am wrong for CMOS, where floating inputs can be either high or
low.

Also, please bottom post.

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thanks , i was wrong . i checked it out. then what about the question If suppose I take TTL AND gate.Then both 4.8V and 5V are considered as high.Obviously the AND output would be High.Now please tell me whether the output will be 4.8V or 5V. that novice asked. pls tell me abt that.thans a lot

If you cannot read and understand the previous posts then the answer is that you need to select a different career path. You will not be successful in electronics. I promise you that this is true.

Bob

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hey hey hey i am sorry abt my mistake . u cant advice like that . ive introduced myself as beginner. and if the questions or answers are wrong, just justify urself.we are here to discuss and if u think u are a an expert in electronics prove urself rather than talk more. reply me . no thanks for ur assumption of my career in electronics.

--
http://en.wikipedia.org/wiki/Transistor-transistor_logic

On 2006-07-08, nitin wrote: then what about the question

They already said the output will be somewhere between 2.4 an 5V. This is assuming it's a TTL chip, and it's being used correctly.

Bye. Jasen

Please try to use something resembling normal English - do not use "u" when you mean "you". As a native English speaker, I find that very distracting - I can't imagine the trouble "u" and "urself" will cause those for whom English is a second language.

For bipolar TTL logic circuits, anything above 2.4 volts will be considered a high. I think most parts will produce 3 - 3.5 volts for a high, and around 0.4 volts as a low. (I've been working with this stuff for so long that just looking at signal levels or waveforms, I "know" what is "high" without having to really measure the voltage.)

CMOS logic will produce something over 4.5 volts for a high (assuming

5 volts power supply, and depending on the load the output is driving)

--
Peter Bennett, VE7CEI  
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On 8 Jul 2006 11:10:23 -0700, in message , "nitin" scribed:

Hello. There is no answer to this question:

"Now please tell me whether the output will be 4.8V or 5V."

You must ask a different question.

--

If life seems jolly rotten, there\'s something you\'ve forgotten,
and that\'s to laugh and smile and dance and sing!

hello to everybody I am sorry for those who got hurt there. Now I am known to quite number of members. anyhow thanks for your replies. I am now clear about the TTL devices.