The maximum number of gate inputs is limited due to electrical constraints. It depends on the technology being used. Practical circuit designs strive to either minimize the number of components, the switching latency or the silicon die area. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. What is the maximum number of inputs for any logic gate?
Ask Question. Asked 5 years, 7 months ago. Active 4 years, 6 months ago. Viewed 12k times. Improve this question. Add a comment. Active Oldest Votes. For a high number of inputs, gates are typically composed of several smaller gates.
Improve this answer. Axel Kemper Axel Kemper 8, 2 2 gold badges 27 27 silver badges 50 50 bronze badges. I don't fully understand how this is so.
To change output Y from high to low, the three transistors have to conduct electrical current. Their sum of internal resistances determines the time needed to unload the output capacitance. A circuit with three transistors in series needs longer than a circuit with just two transistors.
Therefore, the number of inputs has an increasing impact on the latency for a falling edge at the gate output. A NOR gate can have two or more inputs, its output is true if no inputs are true. EX clusive- OR. This is like an OR gate but excluding both inputs being true.
EX-OR gates can only have 2 inputs. EX clusive- NOR. This is an EX-OR gate with the output inverted, as shown by the 'o' on the symbol output.
EX-NOR gates can only have 2 inputs. Logic gates can be combined to produce more complex functions. Truth tables can be used to work out the function of a combination of gates such as the system shown below:.
Begin by creating a table showing all possible combinations of inputs A, B and C in this example with enough extra columns for each intermediate output D and E in this example as well as the final output Q.
Then work out all the intermediate output states, filling in the table as you do go. These intermediate outputs form the inputs to the next gate or gates so you can use these to work out the next output s , in this example that is for the final output Q. This can be wasteful if only a few gates are required unless they are all the same type.
To avoid using too many ICs you can reduce the number of gate inputs or substitute one type of gate for another. The number of inputs to a gate can be reduced by connecting two or more inputs together.
The diagram shows this for a 2-input NAND gate. Then simplify the system by deleting adjacent pairs of NOT gates marked X above. This can be done because the second NOT gate cancels the action of the first:. This is better than the original system which required three ICs one for each type of gate.
Substituting NAND or NOR gates does not always increase the number of gates, but when it does as in this example the increase is usually only one or two gates. The real benefit is reducing the number of ICs required by using just one type of gate. Next Page: Counting Circuits Study.
Note that logic gates are not always required because simple logic functions can be performed with switches or diodes, for example: Switches in series AND function Switches in parallel OR function Combining IC outputs with diodes OR function. There are two series of symbols for logic gates. Traditional IEC. Summary truth tables These summary truth tables below show the output states for all types of 2-input and 3-input gates.
Logic gates are available on ICs chips which usually contain several gates of the same type, for example the IC contains four 2-input NOR gates. There are several families of logic ICs and they can be split into two groups: the series and the 74 Series To compare the different families see the ICs page. Traditional symbol IEC symbol.
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