[sdiy] (oops) EN #76 question

[Tim Ressel]

I have a PDF of the page from EN. Is it kosher to post it here?





Tim Ressel
Circuit Abbey
503-750-9331
timr at circuitabbey.com




________________________________
From: Neil Johnson <neil.johnson97 at ntlworld.com>
To: synth-diy at dropmix.xs4all.nl 
Sent: Monday, November 26, 2012 11:43 AM
Subject: Re: [sdiy] (oops) EN #76 question

Tim Ressel wrote:
> I am looking at Electronotes #76 figures 8a and 8b. 8a shows an 8-bit dac made from discrete binary-weighted resistors. We've all seen this type of dac.
> 
> Figure
>   8b shows a dac that has gaussian distribution. The thing is, this
> circuit will only produce 8 different levels, as opposed to the 256
> levels of the 8a circuit. Am I missing something here?

Its the usual trick for generating a sine wave with pseudo better than 8 bits resolution, by sacrificing other waveforms.  You feed in a bit pattern that turns on multiple 'bits', which then sum to give each sample of the sine wave.  So what you're seeing is not a Gaussian distribution but a sine wave.

Neil
-- Modules and more :: www.cesyg.com
Homepage :: www.njohnson.co.uk ::
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