Analog circuits

An analog circuit works with signals that vary continuously over a range of values, in contrast to digital circuits, which represent information using discrete levels. In an analog signal, quantities such as voltage and current can take any value within their limits, and the circuit's job is to amplify, shape, combine or otherwise process that smoothly changing waveform. Sound, radio waves and the outputs of many sensors are naturally analog, so analog electronics underlies a large part of everyday equipment.

Analog design is built around a handful of recurring functions. Amplifiers and preamplifiers raise the strength of weak signals; filters pass some frequencies while attenuating others; oscillators generate periodic waveforms; and mixers and modulators combine signals, as in radio transmitters and receivers. Power-related analog circuits, such as regulated power supplies and light dimmers, control the delivery of energy to a load. These functions are realized with components like resistors, capacitors, inductors, diodes, transistors and operational amplifiers.

Because analog signals are continuous, the precise behavior of each component matters: tolerances, noise, distortion and temperature drift all affect performance. Designers pay attention to keeping a faithful relationship between input and output, minimizing unwanted noise, and ensuring stability. Many practical systems are mixed-signal, combining analog front ends — which interface with the physical world — with digital sections that process or store the information. Collections of analog circuit examples cover audio, radio, instrumentation and power, and serve as a foundation for understanding more complex designs.

Frequently asked questions

How does an analog circuit differ from a digital one?

An analog circuit handles continuously varying signals, whereas a digital circuit represents information with discrete levels.

What are common analog circuit functions?

Amplification, filtering, oscillation, mixing and modulation, and the regulation of power to a load.

Why are component tolerances important in analog design?

Because the output varies continuously with the input, small variations, noise and drift can directly affect signal accuracy.