[sdiy] Can google's free* 180nm OSHW foundry be used for synth parts?

[usenet at teply.info]

On 06.08.22 15:18, cheater cheater via Synth-diy wrote:
> 
> A friend who works at a semiconductor fab told me that the process
> might not support bipolar transistors (he just doesn't know if it
> does), but I'm not sure how necessary those are for the purpose of
> creating audio chips?
> 
As far as I can see after having a *VERY* short look at the open source 
PDK on github, this process seems to be plain MOS. If it had "proper" 
Bipolars integrated, it would be called BiCMOS.
*AND* the mentioned 10V devices seem to be LDMOS, so they will support 
10V operation only at drain-source, gate-source likely will be limited 
to much less, probably around 2.5V maximum, maybe even less.
*IF* you know what you're doing, one could use some parasitic Bipolars 
intrinsic to how the MOS device is done, but their performance will be 
very poor in about every regard you could think of:
Current Gain? *VERY* low. Probably will be below 10 (yes, ten, but more 
likely something smallish single-digit. I wouldn't bet on more than 
maybe 3...)
Breakdown Voltage? low, probably less than 20V.
Reproducability? poor, even though matching on a chip should be 
reasonable, you'll never know if the next batch will come out the same...
AND: no simulation models, no ready-to-use schmatic or layout elements, 
no LVS (Layout-versus-schematic) verification, probably no support for 
Design Rule Check, so likely a bunch of design rule violations which 
might even cause rejection of the design.

But: I'm not too familiar with GlobalFoundries process offerings, it 
might be that they also have 180nm BiCMOS available, and that might even 
be compatible with the 180MCU open source offering. But that I can't 
tell with what I have avalable.

So in total, I'd say it would be a lot of work, probably a few design 
respins *AND* a bunch of luck to get something out of it that's useful 
for SDIY purposes besides the obvious digital parts the process has been 
optimized for.

Bests,
Florian