digital and analog

GTeclips

Joined Feb 18, 2012
96
I hear these two terms tossed around a lot, but I don't really understand them. I know that they are two different methods of circuitry, but my understanding stops there. I have searched random websites and threads, but I still don't understand the difference. Can anyone give me the big picture of what the difference between analog and digital circuits are, and what situations they might be better than each other in? Thank you!

MrChips

Joined Oct 2, 2009
19,154
This is a common question and it is not easy for the uninitiated to grasp.

All digital signals are analog.

Analog signals are not digital.

Even more confused?

An analog signal gives a range of readings. For example, I like my toast on the light brown side, not white, but with a bit of tan to it, not brown all over. Now that is an analog discription of the colour of my toast. (btw, I prefer whole wheat bread).

But my toaster oven offers me seven settings, 1 - 2 - 3 - 4 - 5 - 6 - 7.
I would really prefer something in between setting 3 and 4 but the toaster does not allow me to choose that. So I have to settle for a setting of 4. That is the example of digital.

In summary, an analog circuit gives you infinite choices in between the lowest and highest values.

A digital circuit sets thresholds that says, anything below this value is raw uncooked and anything above this value is burnt.
If it is in between, we send it back to the kitchen.

Get it?

Last edited:

thatoneguy

Joined Feb 19, 2009
6,349
Digital tend to take an input and interpret it as either a zero or a one, with voltages of 0V and 5V meaning zero and "1", though 0 and 1.2V are 0 and 1 inside a CPU, the 3.3V logic uses 3.3V as high, and 0 for low, saves on power.

There are a ton of different logic families, the majority is CMOS.

Analog is comprised of circuit elements that do not quantize to a specific value, such as an audio source. Many frequencies can be mixed, at different volumes, and the circuits simply amplify or modify the waveform as requested. There aren't really any voltage limits on analog, usually +/- 50V is used in a modest home amplifier for power rails, using dual supplies for both "halves" of a soundwave.

There are many hybrids, such as MP3, which take digital, decompress using a special purpose decompression specific CPU (ASIC or Application Specific Integrated Circuit), then convert the result to analog for human ears.

Many home stereo systems also have the mostly analog path, but also a DSP, or Digital Signal Processor, to add delays or act as an equalizer, etc.

In each case, there is a DAC (Digital to Analog Converter) and an ADC (Analog to digital converter) between the input and output. Most radio is still all analog, but like TV, it may be switching to digital to free up bandwidth and give better sound quality at the same time. The difference is about the same step up as a metal cassette tape with Dolby noise reduction vs. CD.

All digital circuits run on analog principles, though digital circuits use those principles to quantize information to bits, while analog allows the full range without any "stair-steps".

JDT

Joined Feb 12, 2009
658
To generalise, digital is numbers and usually in electronics - binary numbers. A single binary number is a bit: 0 or 1, off or on, low voltage or high voltage. Analog is a continuous level.

For example, in your car the throttle pedal is analog with a continuously variable setting. The light switch is digital: fully on or off.

Complex analog things such as audio can be represented digitally by using many binary bits. For example on a CD the audio is represented using 16 bits. This gives 65536 separate levels. Does not seem a lot but our ears can't tell the difference.

The advantage of digital is that it can be transmitted and stored without error. Extra bits can be transmitted so that even if bits get changed, the change can be detected and restored.

An analog value, however is very sensitive to noise and variations in the system - in fact it is never transmitted unchanged.

The disadvantage of representing analog information as digital is that in the process of converting analog to digital some information is lost. The continuously variable value is split into a fixed number of individual steps.

BillB3857

Joined Feb 28, 2009
2,493
A picture is worth a thousand words. Analog on the left, digital on the right.

Attachments

• 1 KB Views: 48

GTeclips

Joined Feb 18, 2012
96
Thanks for the help guys! It appears this is far more complex than I thought, but I think I have the generally idea. I will have to look into this a bit more. (nerdy pun for those of you who missed it) Again thanks for the help.

VoodooMojo

Joined Nov 28, 2009
495
I am glad we did not take this into the world of 'fuzzy logic'

There are 10 types of people in the world: Those who understand binary, and those who don't.

crutschow

Joined Mar 14, 2008
23,140
I am glad we did not take this into the world of 'fuzzy logic'
But you just did.

Fuzzy logic is still digital. It is just an interesting (and often efficient) way to design control loops that may have non-linear or hard to quantify variables.

GTeclips

Joined Feb 18, 2012
96

bertus

Joined Apr 5, 2008
19,939
Hello,

Take a look at this page for some info on fuzzy logic:
http://www.fuzzytech.com/

This is written there about fuzzy logic:
Fuzzy Application Library/What is Fuzzy Logic?

This introduction is kept brief. You find introductory literature in the Fuzzy Logic Literature section. Complete introductory literature is also contained with all fuzzyTECH products.

What is Fuzzy Logic?

How can a logic which is "fuzzy" be useful? Professor Lotfi Zadeh, the inventor of fuzzy logic, contends that a computer cannot solve problems as well as human experts unless it is able to think in the characteristic manner of a human being.

As humans, we often rely on imprecise expressions like "usually", "expensive", or "far". But the comprehension of a computer is limited to a black-white, everything-or-nothing, or true-false mode of thinking. In this context, Lotfi Zadeh emphasizes the fact that we easily let ourselves be dragged along by a desire to attain the highest possible precision without paying attention to the imprecise character of reality.

There are many subjects which do not fit into the precise categories of the conventional set theory: The set of "all triangles" or "all the guys named John" is easy to handle with conventional theory. Either somebody's name is John or it is not. There is no other status in between. The set of "all intelligent researchers" or "all the people with an expensive car", however, is much more complicated and cannot be handled easily by a "digital" mode of thinking. This is because of the fact that there is no way to define a precise threshold to represent a vague and blurry boundary: there are some obviously expensive cars, like the Rolls-Royce, but many others could be fit into this category as well, depending on how much money you have, where you live, and how you feel!

Why use fuzzyTECH ?

As mentioned before, within conventional logic, terms can be only "true" or "false". Fuzzy logic allows a generalization of conventional logic. It provides for terms between "true" and "false" like "almost true" or "partially false". Therefore, fuzzy logic cannot be directly processed on computers but must be emulated by special code.

This what what fuzzyTECH brings to the party. fuzzyTECH on one hand provides you with all the tools to design and test a fuzzy logic system. Once designed, fuzzyTECH stores your work as an FTL format file. FTL stands for "Fuzzy Technology Language", and can be considered "the programming language of fuzzy logic". Because fuzzyTECH provides an all-graphical user interface, however, you never need to program a single line of code in FTL. Rather, fuzzyTECH on the other hand converts this FTL description to code that can be used on your target hardware that is, the hardware where your fuzzy logic solution finally shall run on.

Designing a fuzzy logic system is different from conventional coding. To give you the most efficient start, fuzzyTECH features three "Fuzzy Design Wizards" that guides you step-by-step. As a beginner, this insures that you have covered all design steps thouroughly, as an experienced developer you will be able to design the prototype of a complex system in just a few minutes.

In addition to the common methods of fuzzy logic, there are various expanded fuzzy technologies which have proven to be very useful. Most fuzzyTECH products support such Advanced Fuzzy Technologies:

Support of normalized rule sets
If you have complex applications, you can easily cause confusing rules using different operators, a chaos of parentheses and complicated "if-then-else" statements. Such constructs destroy the actual advantages of fuzzy logic systems, like clarity and easy expansion. fuzzyTECH uses a different approach by providing normalized rule sets and graphical structure editors. Even the most complex compositions, which must be handled within the rule syntax by other fuzzy logic tools, can be easily developed graphically with fuzzyTECH. Applying normalized rule sets has the additional advantage that the rules can be transformed automatically and developed easily in matrix form, which is often more readable than text or table form in the case of huge and complex systems.fuzzyTECH provides all three presentation forms (text, table, and matrix), while also allowing for switching between them or using them in mixed formats.

Inference methods
Aside from the standard fuzzy inference methods (MAX-MIN, MAX-PROD), most fuzzyTECH products support the advanced Fuzzy Associative Map inference. FAM is an extension of fuzzy inference which was developed out of the combination of neural technology and fuzzy logic. It allows more accurate tuning of the rule bases according to the prerequisites, and as a result, it reduces the often necessary selection procedures of the rules. fuzzyTECH supports not only the maximum operator for result aggregation, but also the BSUM operator (Bounded-Sum). This operator also considers the so-called "support rules" which support the current firing rule.
The fuzzy inference of fuzzyTECH represents a combination of forward/backward chaining which is totally transparent for the user. fuzzyTECH automatically decides the best processing method appropriate to the current fuzzy logic system.

Fuzzy operators
Most fuzzyTECH products provide families of generalized operators for fuzzy inference, from which you can create a desired operator through free parameterization of the available operators. There are three operator families available: Min-Max, Avg-Max, and Gamma. The Min-Max family represents a generalization of the "traditional" fuzzy operators that can also be created as a special case of Min-Max. Through broad empirical research, we now know that the Gamma families are able to represent the human characteristics of decision behavior the best. Through free parameterization you can individually modify your Gamma operators to achieve the optimum of your desired system. The Avg-Max family is an approximation of the Gamma operator family, optimized with regards to computing efficiency. Especially in cases requiring the processing of huge amounts of data in a short time, you may choose the Avg-Max operators, thereby giving up some of the higher accuracy provided by the Gamma operators.
This is a link from the EDUCYPEDIA on digital topics: