Signals in electronics – Analog and Digital types of signals


Signals in electronics – processes of changing a certain physical quantity or state of a physical object over time or in space. The signal depending on its purpose is a carrier of different information e.g. electrical, magnetic and acoustic signals and contains an information parameter e.g. amplitude, frequency (forwards-backwards cycles per second) or pulse width. In electronics the most important signals are the changes in electrical charge, current, voltage and electromagnetic field. They are used to analyze the behavior of electronic circuits or to measure the changing electrical values.

Periodic signal

The periodic signal is a signal that is repeatable at the same time intervals. These intervals are called period „T” of the signal.

Example of the periodic signal

Example of the periodic signal

Types of signals in electronics

In electronics, we distinguish between several types of signals, including:

  • Analog signals – continuous in values and time,

  • Sampled signals – continuous in values, discrete in time,

  • Quantizated signals – discrete in values, continuous in time,

  • Digital signals – discrete in values and time.

Example of the signal conversion from analog to digital form. This is how Analog/Digital Converter (ADC) works.

Examples of analog signals in electronics

  • Sine signal – is described by two parameters: amplitude and frequency. The following equation is also its description:

If we assume that ω = 2πf, then the sine signal can be described by the following formula:

Sometimes, instead of amplitude, the concept of root mean square (RMS) voltage VRMS or peak-to-peak voltage Vpp is used. The RMS value is equal to the product of the peak voltage and √2:

The peak-to-peak value is equal to the doubled value of amplitude Vpeak (peak voltage):

RMS values are used when calculating energy or power. When measuring voltage and current multimeters usually show RMS values.

Example of the sine wave

Example of the sine wave

  • Square signal – like the sine signal it is described by two parameters: amplitude and frequency, with the difference that the RMS voltage value for the rectangular wave is equal to its amplitude. Frequency is often replaced by the period “T” which equals to:

The square signal consists of rising edge, high level, falling edge and low level. Square signals can be „commonly seen” only with positive halves, which means that the low signal level is close to 0V.

Square signals are used both in digital electronics and in the borderline with analog electronics in such systems as: comparators, A/D or D/A converters.

The real shape of the wave differs from the ideal shape of the slope, since they will never be completely perpendicular.

Example of the ideal square wave

Example of the ideal square wave

Example of the real square signal

Example of the real square signal

  • Triangular signal – a triangular wave, that is rising and falling linearly at a certain speed. It can be obtained (in a very simplified way) by the integration of the rectangular waveform.

Example of the triangular wave

Example of the triangular wave

  • Sawtooth signal – as the name suggests, it resembles the shape of a saw tooth. This signal has a linear waveform – the voltage changes at a fixed speed to a certain value and is repeated periodically.

Example of the sawtooth signal

Example of the sawtooth signal

  • Noise – is an intrinsic component of each signal and is generally not desired in electronic circuits.

Example of the noise signal

Example of the noise signal

  • Pulse signals – most of them are not periodic signals. They are described by two parameters: the amplitude and the width of these pulses. Pulse signals are divided into positive and negative. In case of digital electronics, we will also need to analyze periodic pulses, which are further described by frequency and fullness factor.

Example of a rectangular pulse

Examples of positive pulses

Examples of negative pulses

  • Unit steps and spike signals – it can be stated that these signals are not practically used in electronic systems but are used for their description and analysis.

Example of the unit step – part of the square signal

Example of the spike signal – very narrow pulse

Example of the digital signal in electronics

The following illustration shows a digital signal consisting of four 3-bit words in binary code.

Example of the digital signal – binary code


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I’m Michael. Me and my friend John are students of electronics. We are creating this site to help students and any interested people understand electronics.

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