[sdiy] $100 Chip fab service

[Ben Bradley]

I'm wondering what you can do in 1.8V "180nm CMOS technology" that's
not digital. Does anyone even have the analog characteristics of such
small N-channel and P-channel mosfets (and no BJTs, the heart of just
about any exponential converter)? I'm guessing they only have specs
for required voltage levels for 0 and 1, switching times and fanout
and such.

On Tue, May 1, 2018 at 1:17 PM, cheater00 cheater00 <cheater00 at gmail.com> wrote:
> Who said everything has to be digital? Just the output must be digital. You
> could use an ADC and DAC to bridge over the bus.
>
> And yeah, 1.8V, doesn't matter for the inner life of the chip anyways, it's
> not like you must run synth circuits at +/-15V
>
>
> On Tue, 1 May 2018 16:26 Eric Brombaugh, <ebrombaugh1 at cox.net> wrote:
>>
>> On 05/01/2018 07:16 AM, Neil Johnson wrote:
>> > Hi,
>> >
>> > On 1 May 2018 at 12:55, cheater00 cheater00 <cheater00 at gmail.com> wrote:
>> >> So apparently the people behind RISC V want to start a service where
>> >> you can
>> >> send your chip designs in and get them made. I wonder if this would be
>> >> useful for analog.. this could really launch analog synths into the
>> >> stratosphere. Perfect replacements for old rare chips, great new
>> >> designs,
>> >> better OTAs, oscillators, envelopes, amps... sounds almost too good to
>> >> be
>> >> true, so there's good reason to follow this.
>> >>
>> >> Bear in mind this has loads of transistors.. so you could easily fit
>> >> multiple (16? 64?) complex synth voices plus fx plus a micro to control
>> >> them
>> >> on one $100 chip and have all sorts of IO, too (probably best muxed as
>> >> a
>> >> single serial line to use as few pins as possible)
>> >>
>> >> https://hackaday.io/project/152709-itsy-chipsy-make-your-own-100-chip
>> >
>> > It is supposedly 180nm.  In which case forget about anything above a
>> > few volts (typically 1.8V, or maybe up to 5V if you really push it).
>> >
>> > http://www.onsemi.com/PowerSolutions/content.do?id=16678
>>
>> Also - $100 gets you 1/64th of the whole die and *no* I/O pins (you must
>> share the common power/SPI/JTAG buses).
>>
>> Thanks, but if I'm going to have to do everything digital anyway I'll
>> stick with cheap FPGAs - at least there I can iterate a design without
>> blowing a hundred bucks for every pass.
>>
>> Eric
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