
Do-it-Yourself ASICs (2013) - omgwtfbyobbq
https://www.analog.com/en/analog-dialogue/raqs/raq-issue-95.html#
======
tyingq
I'm sure I'm missing something. This is saying, for analog, if you can't find
the right IC, then build that part of the circuit from discrete components.

That's true, but seems obvious, and I don't know of a practical general
alternative for low volumes.

~~~
jimmyswimmy
It's kind of funny; I came out of school ready to design circuits with
discrete transistors and they laughed at me. "Sure, that can work, but it will
definitely work if you use this opamp." Much like we caution people not to
write assembly, because the compiler can do it better.

But sometimes it can't. Sometimes the opamp designers made choices I would not
prefer for my circuits. To me it's funny how after all this time, I've only
recently started to consider transistor-level design again. I suspect it's a
deeper understanding of the tradeoffs than I had as a novice engineer. Or
hubris, thinking I can do it better.

There absolutely isn't a practical alternative for low volumes, there's barely
even one for medium volumes. There once were IC houses with semicustom parts -
they had a variety of transistors, resistors and maybe a few (really huge
bipolar) gates onboard, and you could design the metal layer, resulting in a
single custom mask on an otherwise standard product. Actually, Astec still has
one, Device Engineering offer one, but there's not a lot out there. This was
always a niche business anyway.

So yeah, it does seem obvious that we should design from discretes, actually
crawl into the boxes in our block diagrams and build the things in there from
scratch. But it's funny how easy it can be to stop doing that, to just find a
single chip/module that does it all. And it's been amazing to me how well the
IC market has mapped out to what I have needed over the past several years.
Every time I've tried to build something, I found I could just buy it.
Eventually, you think "buy" before "build." For me, it's taken extra effort to
consider "build" first anymore.

Just like the author found, it's fun, too. Just buying that ublox GPS chip is
okay, but building the parts I need is cool.

~~~
JamesBryant
But don't waste time reinventing the wheel. I needed a small audio amplifier
the other day and looked for an IC to build it. My junk box was empty of audio
amplifiers so I went to a distributor and found a nice IC for 65p but minimum
order 10 off. With postage the price was about £10, and I still had to find
the other components and build it.

I was just about to order it when I realised it might be cheaper on eBay.
There a found an assembled board with the same amplifier for 56p with a
minimum order of 5 pieces:- £2.80 post paid and ready to use - and four spare
ready-made amps for future projects.

Beating the system is fun, too.

~~~
kevin_thibedeau
The eBay sourced chips are likely counterfeits that won't meet all the specs.

~~~
omgwtfbyobbq
In my experience the random stuff I buy off of whatever $Auction_Site seems
identical to what I buy from $Local_Vendor, but with no QA or packaging. The
defect/failure rate is higher and it takes a lot more time to arrive, but the
cost is significantly less.

It's possible that there are more counterfeits, but I don't think the stuff
off of $Auction_Site is likely (>50% chance) to be a counterfeit just because
it's from $Auction_Site.

~~~
kevin_thibedeau
If it's a chip that you can search for in a product description it has a high
enough profile to be an SZ fake. See this example of a fake signal gen IC that
almost works properly:

[https://www.youtube.com/watch?v=02XtneCHnDA](https://www.youtube.com/watch?v=02XtneCHnDA)

Add in a price that's too good to be true and the odds go up.

~~~
omgwtfbyobbq
I can see that. I've purchased several laptop batteries that likely used old
cells pulled from another laptop or whatever. At the same time, I don't mind
that the runtime is a 1/2 to 3/4 of a new battery when the price is 1/5 of a
new battery.

------
klhugo
Design is not all. There is a reason IC design houses are vanishing, it is too
expensive to design custom chips. Only large companies can afford the
tapeouts, testing, Packaging, and large volume production.

~~~
nanomonkey
Any idea what parts are too expensive, and why? One would think that over time
tapeout would have more and more processes automated, as with some testing.
Packaging could be made standardize as much as possible. Thanks.

~~~
satya71
Competitive performance requires access to latest technology. Those are super
expensive.

~~~
5436436347
Purely analog circuits, including those with digital functions as an ancillary
feature, are never on the latest process node. Analog functions don’t scale
down well, high drive currents or voltage support require minimum feature
sizes. The notable increase per node in terms of frequency support would be
wasted even on parts operating up to the gigahertz range. Even the most
aggressive analog circuits, like current RF-CMOS designs, are only released
when the node is a few generations old. The process control required to get
them functional within usable tolerances for analog circuits like current
mirrors and differential pairs is greater than what digital designs demand

------
panpanna
Off topic: the cookie dialog in this site is a textbook example of dark
patterns.

On topic: the article basically says you don't need your own asic since you
can but whatever you need as discrete ICs from them??

