Are BBD chips considered Analog or Digital, or even neither or both?

[StephenGiles]

I wonder if you can catch covid more easily when using a digital chorus!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[merlinb]

Merlinb, what is the RAM storing, then? Whatever it is, it must be binary, somehow?

It's just clocking the bitstream through a serial shift register.

[bushidov]

Merlinb, does that mean the bitstream is holding the voltage values at a digitized value (0 - 1023, assuming it's a 10 bit ADC) per quantized time value?

[merlinb]

Merlinb, does that mean the bitstream is holding the voltage values at a digitized value (0 - 1023, assuming it's a 10 bit ADC) per quantized time value?

It's a 1-bit DAC, so the only 'values' are 0 and 1. It's very much a 'yang' to the BBD's 'ying' way of doing things. Easier to explain in pictures:
https://www.beis.de/Elektronik/DeltaSigma/DeltaSigma.html

[bushidov]

Ah, so instead of the RAM holding a single multibit value per quantized time unit, it has multiple single bit values that the order of the string of bits make up the single shape of the analog curve over time. That's a good way to get more resolution with less RAM. And the shift registers bit width resolves the "CPU time" for "calculation", as now it doesn't have to calculate anything, but rather just shift it out pieces at a time for analog filters to re-round out as analog curves. That's pretty cool.

[amz-fx]

An example circuit...



MC3302P is a quad analog comparator IC.  The Vin is an analog signal and D0-D3 are analog comparator outputs that will vary in a binary count as the Vin changes. They are not even sampled since they will flip around as the analog signal exceeds the various comparator thresholds. There is no clock driver.

The Vin input signal is analog and the four outputs are analog, however, this is an analog-to-digital converter. The D outputs are either low or high analog voltages.

If I take D3 and output it as an audio signal, I will get a fuzz tone. Analog?  If I store the states of the D0-D3 as ones or zeros, it has become digital? What if I store the output of D0-D3 on capacitors and then mix their voltages in an inverting opamp with weighted resistor values to recreate the Vin signal? Where did it become or not become digital? The dividing line is a little fuzzy here...

Best regards, Jack 

ps: This is an actual circuit that has had commercial use.

[bushidov]

he dividing line is a little fuzzy here...

I see what you did there. 😏

[amz-fx]

"A man who would make a pun, would pick a pocket." - Samuel Johnson

   

-Jack

[Fancy Lime]

So what about the PT2399? I've heard those referred to as digital and analog, also.

The PT2399 uses sigma modulation, so it's the same quandry as the BBD; neither truly digital nor definitely analog. The analog is encoded in a bit stream but not as discrete digital numbers, rather as the average integrated value of the stream. I've said before "the PT2399 is as analog as any BBD... just in a different way" !

Huh, I didn't know that. Thanks for the explanation!

Andy