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-   -   Tda1541a minus the DEM caps? (http://www.diyaudio.com/forums/digital-source/222666-tda1541a-minus-dem-caps.html)

ash_dac 1st November 2012 07:32 PM

Tda1541a minus the DEM caps?
 
Ok so I've been away from here for years due to partly career focus, and also the wife banning from doing any diy audio.

Anyway this old patent from van de Plassche mentions replacing the DEM caps with some kind of integrator switched capacitor type implementation. That's my reading anyway.

Digital/analog converter with capacitor-free elimination of a.c. components . Rudy J. van de Plassche Patent US4703310 - Digital/analog converter with capacitor-free elimination of a.c. components - Google Patents

Has anyone tried this? It being patented I guess the end result entered a mainstream production chip (maybe the CS4397?) or scaled down tda1541a?

martin clark 2nd November 2012 01:05 PM

R J van der Plassche wrote a book on cmos ADC/DACs around this time...I 'm guessing the patent you link is related to Philip's development of cmos dacs around then - look at the lower votage requirements compared with the multibit devices. IIRC the TDA1305 datasheet has a note on the continuous claibration technique from memory. I havent compared the two documents, might do later.

ash_dac 11th November 2012 07:46 PM

Thanks. I did a search for 'van de Plassche tda1541a' in that famous search engine and it produced a link to what looks like his university course text.

Aside from the copyright issues everything was there (DEM, switched capacitor Dacs, digital/ analogue filtering, 1-bit DACs, . A really interesting read , if a little beyond me, but yeah it's clear it's CMOS.


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