analog circuit electronic circuit that operates with currents and voltages that vary continuously with time and have no abrupt transitions between levels. Generally speaking, analog circuits are contrasted with digital circuits , which function as though currents or voltages exist only at one of a set of discrete levels, all transitions between levels being ignored. Since most physical quantities, e.g., velocity and temperature, vary continuously, as does audio, an analog circuit provides the best means of representing them. However, digital circuits are often preferred because of the ease with which their outputs can be manipulated by computers, and because digital signals are more robust and less subject to transmission errors. There are special analog-to-digital and digital-to-analog circuits to convert from one type of signal to the other.
Since the information is encoded differently in analogue and digital electronics, the way they process a signal is consequently different. All operations that can be performed on an analogue signal such as amplification, filtering, limiting, and others, can also be duplicated in the digital domain.
The first electronic devices invented and mass produced were analogue. The use of microelectronics has reduced the cost of digital techniques and now make digital methods feasible and cost-effective.
The main differences between analogue and digital electronics are listed below:
Because of the way information is encoded in analogue circuits, they are much more susceptible to noise than digital circuits, since a small change in the signal can represent a significant change in the information present in the signal and can cause the information present to be lost. Since digital signals take on one of only two different values, a disturbance would have to be about one-half the magnitude of the digital signal to cause an error; this property of digital circuits can be exploited to make signal processing noise-resistant. In digital electronics, because the information is quantized, as long as the signal stays inside a range of values, it represents the same information. Digital circuits use this principle to regenerate the signal at each logic gate, lessening or removing noise.
A number of factors affect how precise a signal is, mainly the noise present in the original signal and the noise added by processing. See signal-to-noise ratio. Fundamental physical limits such as the shot noise in components limits the resolution of analogue signals. In digital electronics additional precision is obtained by using additional digits to represent the signal; the practical limit in the number of digits is determined by the performance of the analogue to digital converters, since digital operations can usually be performed without loss of precision.
Digital systems require less skill and therefore are much easier to design than comparable analogue circuits. This is one of the main reasons why digital systems are more common than analog. An analogue circuit must be designed by hand, and the process is much less automated than for digital systems.