[sdiy] Designing Analog ICs

[Tom Wiltshire]

Ok, so if this type of approach (resurrect genuine analog ICs) is out of reach, are there ways we could create 'virtual analog' ICs?

This is essentially what I was trying to do with my PIC projects some years ago. Take a digital chip with analog I/O and hide all the digital stuff inside the chip, so that from a users point of view, it acts just like an analog chip. I was reasonably successful for low-speed modulation stuff, even using only a $1.50 PIC.

What technology would I be looking at to do the same for audio? At 96KHz? At 192KHz/24-bit? FPGA?

It seems to me that digital stuff has got good enough now that you *can* build something which is functionally identical. People always go "Ah, but what about the interesting non-linearities that analog introduces? Digital is always too clean..." but that argument doesn't really hold water any more, since you can accurately model whatever non-linearities you want too. It's a lot more work than building a clean design, but it's possible - the history of the digital Moog filter emulation is essentially that process.

Is there a configurable/programmable chip out there with high quality audio ADC/DAC at either end?

It has to be a one-chip solution, or the whole point is missed. I can build a digital audio processor circuit now by sticking a codec on a processor and etcetc - we're talking about a virtual analog SSM2040 filter chip, with input/output for analog audio, and ADC channels for CVs.

Anyone know of such a thing?

Thanks,
Tom


On 7 Sep 2011, at 04:33, David Schwan wrote:

> Several comments:
> 
> 1) Mosis does support the kind of old bipolar process needed for most Synth DIY chips. Even if Mosis did support the right process, it would cost $10K - $15K for 40 parts.
> 
> 2) Tooling costs will be about $2K per layer, with maybe 13-14 layers max. 
> 
> 3) One engineering lot could be 10-20 wafers, $400 to $500 a wafer. Likely 6" wafers
> 
> 4) Packaging? I have no idea what the cost is.
> 
> 5) What you likely need is a 40V bipolar process with device models. Preferred is 2 layers of Metal. Needs to have some form of capacitor, and two types of resistors, hopefully with opposite tempco's
> 
> 6) Electric Editor is built for CMOS, not bipolar.
> 
> 7) Assume versions A and B don't work. Assume that they can be tweaked with Metal layers only.
> 
> 8) You will need to write a DRC rule deck for some tool.
> 
> 9) Since this is Bipolar, LVS will be hand checked.
> 
> 10) This design is not like doing a PCB, If you haven't done it before you're in for a real learning experience.
> 
> 
> Note: 
> I have 30 years experience designing analog and RF chips including old stuff like 40V bipolar.
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