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#### Phil Hobbs

- Jan 1, 1970

- 0

Well, if we generously assume that an ADC that fast could have a 5V

input range, 1 LSB at 20 bits is 5 uV, and the quantization noise is

1/sqrt(12) times that, or 1.4 uV. In a 100 MHz bandwidth, that's

140 pV/sqrt(Hz). In real life, the input structure would have to be

several times faster than that in order to settle to that accuracy in

the time available, putting the maximum input noise down in the

50 pV/sqrt(Hz) range, not counting the effects of input capacitance.

Good luck with that.

Cheers

Phil Hobbs

Irritated yelling mode...You have just demonstrated once again WHY I

re-derive EVERYTHING! I NEVER trust 'cookbook' equations, especially

after getting severely burnt by an article in EDN showing 'cookbook'

values for a simple 'what's its name? filter [the simple 5-pole low pass

type using two 2N3904's in series]. Whereupon, I was forced to rederive

ALL the values for both Butterworth AND Tschebyshev(sp?) *and* using an

HP calculator with reverse polish input (spit, spit, curse begone!) I

'optimized' a response to obtain values and voila! worked. But that

little effort caught me on a late Friday [deadline Monday morning] to

make a filter that worked! All weekend!

I HATE PACKAGED FORMULAS!!! I have NO idea what these numbers you gave

me should mean to me.

(Context restored)

Sorry? LOL! I actually read that out loud for effect.

So apart from posturing, what do you actually disagree with, and why?

Cheers

Phil Hobbs

--

Dr Philip C D Hobbs

Principal Consultant

ElectroOptical Innovations LLC

Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203

Briarcliff Manor NY 10510 USA

+1 845 480 2058

hobbs at electrooptical dot net

http://electrooptical.net