1.8.3 Digital integrated circuits
There are many types of digital integrated circuit products. They constitute a variety of logic circuits, such as gate circuits, flip-flops, counters, registers, encoders, decoders and so on. In our computer, there are a large number of various functions of the digital integrated circuits.
Commonly used digital integrated circuits TTL, ECL and CMOS three series. ECL circuit speed, but power consumption, anti-interference ability is weak, generally used in high-speed and low interference circuit; CMOS circuit static power low, wide supply voltage range, simple circuit, high integration, HCMOS circuit Is a high-speed series, so the current large-scale and very large scale integrated circuits in the more widely used (see Figure l.92); TTL circuit is between ECL and CMOS.
A digital circuit is also called a logic circuit. In digital logic, there are normally only two states, Low and High, Zero and One, On and Off, which correspond to the same state, except that the name Different.
Digital circuits are based on "AND", "OR", "NOT", and they are often called "AND" and "NOT". In their input and output between the existence of a specific logical relationship. The tables that show the logical relationship between their inputs and outputs are called truth tables.
Table 1.24 lists the major types of digital logic gates and their truth tables.
In the table, A and B are the inputs, OUT is the output; "1" is high or close to the positive supply voltage, "0" is low or close to ground (negative supply voltage).