Differences Between Analog and Digital Signals: Key Characteristics and Examples

What are the differences between Analog & Digital signal?

Analog Signal is a with with multiple ampletudes like the voice signal, generator output etc
Whereas the digital signal has only two values zero and one like a switch has only two values either zero or one.

An analog signal can also be constant, remember.

Think of a digital signal as a analog signal restricted to two domains, 0 or 1.

yaa right....

The distinction is in how they are interpreted. A digital signal is analog in nature, but is viewed as having only two states: high or low [that can be voltage or current].

Another way of looking at it is: with analog, the voltage or current levels carry the information, as in an audio signal. These levels translate directly when applied, as an audio signal to a speaker.

Digital, carries the information as a set of numbers, encoded as ones and zeros. A digital signal must be decoded before it is physically applied, If you feed a digital signal directly to a speaker, you will get incoherent noise, even if the signal carries the audio information in digital form. This information must be extracted using something like a DAC (Digital to Analog Converter) before it is applied to the physical.

BTW: "zero" and "one" in a digital signal is arbitrary and can be encoded as "high" equals 1 and "low" equals 0 or vice versa. And it's not even zero volts and the maximum voltage. Each logic technology has it's own rules for interpreting ones and zeros. For TTL input signal levels anything between 0.8V and 0.0V is considered a zero, and anything between 2,2V and 5.0V is a one. For CMOS, where VDD is 10V, a zero is anything below 3V and a one is 7V to 10V. ECL considers -1.75V to be a zero and -0.9V to be a one. And, it's even possible to encode more than just two states. Binary is not the only digital base that can be used.

So, digital is analog levels interpreted as digital states.

Great Reply !!

I'm curious what other forms of digital signals besides Binary are commonly used and in what industries or products have you run across them?

Thanks,

Colle

"Qubits" come to mind, in a quantum computer. In a motor system that has forward, stop, and reverse conveyed to it by three distinct voltage levels. You could argue that Tri-state logic is a form of trinary.

Some electronic music keyboards (at least the ones in the old analog synths) encoded the keys note as a discrete voltage on a single line. Thus, if the keyboard had 54 keys, then the digital system was base 54.

Thanks for all of your replies.

the differece is in interpretation, analog signal is viewed as continuous in time/amplitude/frequency/phase, digital signals are viewed discretely, they are sampled in time/amplitude/frequency/phase. in analog domain for voltage of a signal to go from one level to the next it needs time and it needs to pass all the levels in between, in digital domain signals are often viewed discretely in time, at some defined sampling interval so when at time 1 signal is at level A and at time 2 the signal is is at level C for all intents and purposes signal has not passed the level B in between because there is no such sampling time as 1.5