# conversion of digital to analog signal

Discussion in 'The Projects Forum' started by jblueink, Jun 14, 2008.

1. ### jblueink Thread Starter Member

May 27, 2008
24
0
helloo every one i have a question: can an inductor and capacitor in series convert a low frequency digital signal to an analog signal. let say the the frequency is 50hz and the value of the inductor and the capacitor are 1uH and 3300uF respectively.

2. ### bertus Administrator

Apr 5, 2008
15,535
2,302
Hello,

A digital signal can not be converted to analog just by using a inductor and a capacitor.
A digital signal is composed of bits that reprecent the analog value.
When you give this value to a digital/analog convertor the analog signal will apear at the output of this convertor.
On this page on the EDUCYPEDIA there are links to pages and documents about A/D convertors.
http://www.educypedia.be/electronics/digitalconvertors.htm

Greetings,
Bertus

3. ### SgtWookie Expert

Jul 17, 2007
22,182
1,728
Actually Bertus, that's not quite correct.

You can turn a square wave into a pretty decent sine wave by using a low-pass filter. The reason is because a perfect square wave is the sum of all the odd harmonics of a fundamental frequency.

If you run a perfect square wave through a perfect low-pass filter that removes all of the harmonics that are higher than the fundamental, you wind up with a perfect sine wave. Of course, nothing in the real world is perfect. However, you can wind up with a reasonably decent representation of a sine wave.

You're not going to wind up with a great sine wave using a two-pole filter, but it'll make a start.

See the attached analysis. Note the passband and stopband. You're -1dB down at 50Hz, and -3dB at 100Hz. If you added another stage like that, you'd be -2dB at 50Hz, and -6dB at 100Hz.

File size:
35.8 KB
Views:
21
4. ### hgmjr Moderator

Jan 28, 2005
9,030
214
You can see what sgtwookie is refering to by checking out this link to the section in the AAC ebook on squarewave's constituient components.

hgmjr