digital and analog

Discussion in 'Homework Help' started by GTeclips, Mar 1, 2012.

Feb 18, 2012
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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!

2. MrChips Moderator

Oct 2, 2009
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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: Mar 1, 2012
3. thatoneguy AAC Fanatic!

Feb 19, 2009
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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".

4. JDT Well-Known Member

Feb 12, 2009
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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.

5. BillB3857 Senior Member

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

• analog-digital.png
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justtrying and MrChips like this.

Feb 18, 2012
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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.

7. VoodooMojo Active Member

Nov 28, 2009
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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.

8. crutschow Expert

Mar 14, 2008
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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.

Feb 18, 2012
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Apr 5, 2008
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Hello,

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

This is written there about fuzzy logic:
This is a link from the EDUCYPEDIA on digital topics: