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what are logic gates??

A logic gate performs a logical operation on one or more logic inputs and produces a single logic output. The logic normally performed is Boolean logic and is most commonly found in digital circuits. Logic gates are primarily implemented electronically using diodes or transistors, but can also be constructed using electromagnetic relays (relay logic), fluidic logic, pneumatic logic, optics, molecules, or even mechanical elements.

In electronic logic, a logic level is represented by a voltage or current, (which depends on the type of electronic logic in use). Each logic gate requires power so that it can source and sink currents to achieve the correct output voltage. In logic circuit diagrams the power is not shown, but in a full electronic schematic, power connections are required.

The simplest form of electronic logic is diode logic. This allows AND and OR gates to be built, but not inverters, and so is an incomplete form of logic. Further, without some kind of amplification it is not possible to have such basic logic operations cascaded as required for more complex logic functions. To build a functionally complete logic system, relays, valves (vacuum tubes), or transistors can be used. The simplest family of logic gates using bipolar transistors is called resistor-transistor logic (RTL). Unlike diode logic gates, RTL gates can be cascaded indefinitely to produce more complex logic functions. These gates were used in early integrated circuits. For higher speed, the resistors used in RTL were replaced by diodes, leading to diode-transistor logic (DTL). It was then discovered that one transistor could do the job of two diodes in the space of one diode even better, by more quickly switching off the following stage, so transistor-transistor logic, or TTL, was created. In virtually every type of contemporary chip implementation of digital systems, the bipolar transistors have been replaced by complementary field-effect transistors (MOSFETs) to reduce size and power consumption still further, thereby resulting in complementary metal–oxide–semiconductor (CMOS) logic.

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A gate is a digital circuit that follows certain logical relationship between input and output.

The 5 most common logic gates are :- NOT, AND, NAND, OR, NOR.

you can study more about them in Study material of meritnation - class XIIth Semiconductors, Digital Electronics and Logic Gates

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Logic gates are electronic circuits used to perform certain logical operations. The commonly used gates are: AND, OR, NOT, NAND and NOR. Each logic gate is indicated by a symbol and its function is defined by a truth table. The flow of current or signal is controlled using these gates. These are basic components of digital electronic devices

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thanks for clearin my doubts :) tal :)

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are the gates used for treeting the basic logical expressions

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order of output 

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they are the digital circuits used to obtain only a set of output like the truthtables in mathematics.

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the gates which have some logical operation to be applied on it.

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logic gates are gates which hv some logical operation applied to it. it is a part of semi conductors chapter

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Logic gates are used in electronics.
A?logic gate?is an elementary building block of a digital circuit. Most?logic gates?have two inputs and one output. At any given moment, every terminal is in one of the two binary conditions low (0) or high (1), represented by different voltage levels.
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