YADA (yet another discrete ADC) design

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Twenty Log

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Joined
Jan 7, 2010
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213
Location
New Hampshire, USA
Uhg... It's yet another discrete ADC design, currently under way here...  So far, the concentration has been on the quantizer and feedback DAC for the delta-sigma modulator...  H(s) design to ensue later, but am worried that the quantizer is sampling extremely fast (absurd OSR) and that limitations in the performance would be the front end... Proposed as a CIFF design...

first-time bring-up was a little rough (shown), but eventually tuned in nicely after a minute or so of tweaking...

Cheers!
 

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Ah... Good point... perhaps "discrete" should be in quotes ;)

Er... um...  "Non-monolithic ASIC ADC"... but using individual transistors, opamps, capacitors and resistors on the PCB.... Nothing more complex than opamps as ICs...  (yes I suppose the individual transistors are "ICs" as well -- technically...)

Definitely not a "single-chip" ADC solution... The FPGA for the decimation would be more ASIC-esque I suppose...
 
You could make a 1 bit delta-modulation A/D with discrete circuitry but discrete digital memory is unwieldy.

In fact it was an early IC DAC (Burr-Brown)  resistor ladder that made SAR A/D and PCM practical.

I always love these "all-tube " CD players that pop up from time to time.

JR
 
Indeed... I also have a 1950s vintage digital logic book that is all-discrete tube logic circuits!  Awesome read, but...

Additionally, discrete opamps (except for some of those discrete transistors in the design) probably have no place in this design as control system theory rules, where precision, speed and "infinite" gains in the plant are required in feedback loops well into the MHz for this design.

So far, just 2/3 a modulator and then a full ADC with delta-sigma modulation once the FPGA and H(s) portion ensues... 

Anything ubiquitous out there, other than USB that can accept 384kHz PCM?  (e.g., AES/EBU, Ethernet) 

Nuendo can run 384kHz 10 years ago last I knew.. I think ProTools is physically limited (hardware and software) to 192kHz currently.

Cheers
 

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