Shay wrote:

> I study Sigma-delta data converters.  Sigma-delta is a specific type of 
> architecture that works well for 16 to 24-bit applications like audio. A 
> data converter is a specific type of integrated circuit (IC) that 
> converts analog signals to or from digital signals.

IIRC, this involves generating a pulse train from an analogue signal. 
This train consists of negative and positive pulses in such a way that 
if you average them together, you get the original signal. But actually 
to make the converter, you send the pulses to a counter, which then 
converts them into normal binary numbers.

(The pulse train itself has the desirable property that all the pulses 
are "equal". In other words, unlike a binary signal that has a most 
significant bit and a least significant bit, and you need to know which 
bits those are, the pulse train doesn't require any such synchronisation.)

The DSP book I read had a whole chapter on A/D and D/A conversion. 
Apparently A/D conversion actually works better if you deliberately add 
a tiny amount of noise. (For the same reason that POV-Ray purposely adds 
sampling jitter to the antialias pass.)

> The big areas of research in this field are (1) lower power and (2) 
> migrating technologies.

Makes sense...

> In my opinon, data converter design is one the most difficult aspects of 
> IC design.  A good designer has to know analog circuits, digital 
> circuits, signal-processing, and sensors/transducers.  And as long as 
> innovative designs are required, there will be good jobs for high 
> quality engineers.

Heh. It's well beyond my field... ;-)

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