AND gate

From ArticleWorld

In digital electronics, an AND gate refers to a logic circuit with two or more inputs, all of which should be high in order for the output to be high. This means that to each of the input variables, signals must be given simultaneously so that a signal is received at the output variable. The input/output variables can be voltage levels or energizing signals. The AND gate is referred to as a basic gate since other gates can be derived from it.

AND gate hardware

AND gates are basic logic gates, just as the OR and NOT gates. They are recognized by both transistor-transistor logic (TTL) and complimentary metal-oxide semiconductor (CMOS) ICs. The CMOS IC is referred to as the 4081. It has four AND gates, each of which is independent with two input lines. Apart from this, three input 4073 and 4-input 4082 AND gates are also available.

It may so happen that an AND gate is not available for use in a logic circuit. In such a case, an AND gate can be prepared by the combination of two NAND gates. A NAND gate is basically an AND gate with a NOT gate connected to its output, in order to invert its result. NAND gates are considered to be universal gates since any other gate can be prepared by using a combination of two or more of them. In the case of an AND gate, all that is required is the sending of the output of one NAND gate to the short-circuited input of the other NAND gate, resulting in an ‘inversion’ operation taking place. Thus an 8-input NAND gate (4068) can be easily converted to an 8-input AND gate.