Digital Logic Design Online Course - Computer Gates - Digital Logic Gates

Digital Logic Design Online Course

Digital Logic Gates

A digital logic gate is an electronic component that implements logic on an input signal and then outputs a specific output. They serve as the basic building blocks of any digital system, regardless of complexity. Digital logic gates can be divided into two types.

Basic Door

A NOT gate has one input and one output, and the output always inverts (ie, negates) the input.
An AND gate can have multiple inputs, but the output is limited to a single input. If all inputs are high here, the output goes high. Otherwise, the output is low.

The OR gate is a multiple-input, single-output gate, which has the same output as logic '0' when all inputs to the gate are low. For the remainder of the input combination, the higher the input, the higher the output logically.

The NOT, AND, and OR gates are spare gates that are used to realize Boolean expressions. This is called the base gate.

Universal Gates

A NAND gate that is a multi-in, single-out logic gate when an AND gate is used with a NOT gate. This gate keeps the output low only when all inputs are at a logic high level. On the other hand, for other input combinations, the output of the gate is high.
The output here is at logic level '1' only when all inputs to the gate are low. All other combinations of inputs become logical zeros at the gate output.
NAND and NOR gates are considered general purpose gates because all logical functions can be realized using these two gates.

There are also two more gates, XOR and XNOR are used extensively. An XOR gate can have any number of inputs while the output is limited to a single line. For 2-input XOR gates, the output is high only if the inputs are not identical, and the output is low otherwise. For example, if both inputs are 0 and 1, the output is 1. Otherwise, if the inputs are 0 and 0 (or 1 and 1), the output is 0. When XOR is used with a NOT gate, an XNOR gate is created that complements the operation of the XOR. This means that the output of the XNOR gate is high for the same input and low for the non-identical input.

Digital logic gate transistors, diodes and other basic electronic components. However, it can be used commercially as an integrated circuit (IC) using TTL (transistor transistor logic) or CMOS (complementary metal oxide silicon) technology.

This device is 'positive' or 'negative' logic. In a positive logic device, the high voltage level is considered a logic '1' and the zero voltage is a logic '0'. On the other hand, if the device operates as 'negative logic', the high voltage is considered logic 0 and the low voltage is considered logic. All voltages between 2 and 5 V are considered high for TTL, while between 3 and 18 V for CMOS. Likewise, all voltages below 0.8V are considered logic '0' for TTL and '0' for CMOS, which is less than 1.5V.  To overcome this, it is expected that this device will not be affected by external noise.