[sdiy] $100 Chip fab service

cheater00 cheater00 cheater00 at gmail.com
Wed May 2 20:20:23 CEST 2018


Why is the max operating voltage so important? I don't really see the
issue. This doesn't have to directly interface with any other synthesizers.

On Wed, 2 May 2018 20:11 , <mskala at ansuz.sooke.bc.ca> wrote:

> On Wed, 2 May 2018, cheater00 cheater00 wrote:
> > Why would the characteristics differ? They're monolithic on a single
> chip,
> > and chips from different wafers will likely have the exact same
>
> Everything varies in a semiconductor process if it isn't deliberately
> controlled, and if you build something that depends on an unspecified
> parameter and it doesn't work because that parameter changed, too bad -
> you have no recourse, because the manufacturer never promised you that.
>
> > characteristics. Sure, stuff needs to be characterised, but once you have
> > that you're free to go. Bear in mind you get several orders of magnitude
> > more transistors than in a normal synth module.. so this opens a lot of
> > possibilities.
>
> I don't think there's reason to think the transistors in this service will
> ever be accurately characterized with respect to analog parameters,
> because they are not meant to be used that way.
>
> Even in the best case where you know exactly how the transistors behave,
> so what?  As others have commented, they're going to be low-voltage only,
> and you're not going to be able to connect to them from outside the chip
> except through an ADC/DAC combo - and it's not clear how you're going to
> build the ADC and DAC inside the chip at all.  You're unlikely to have any
> real ability to build passives because doing those in a semiconductor
> process is difficult at best and this process isn't designed to do them.
>
> I don't know what kind of "possibilities" this is supposed to open up.
> Digital ones,I guess.  There's overlap with what FPGAs do, but this must
> have some value those don't provide or it wouldn't be offered.  It's
> probably also meant as an educational opportunity for people who are
> learning to design (digital) ICs, in which case the question of whether
> there may be more efficient ways to build the same circuits is not the
> real issue.  Trying to build *analog* stuff with this service seems like
> a pipe dream.
>
> --
> Matthew Skala
> mskala at ansuz.sooke.bc.ca                 People before principles.
> http://ansuz.sooke.bc.ca/
>
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