Chip shortage? DIY: miniaturize transistor based electronics? - Page 1
Forum section: electronics / general

author: RES
author_rank: Regular Contributor
timestamp: April 28, 2022, 08:36:08 pm
content: What if chip shortages keep becoming more of a problem in the future, can hobbyists create their own "chips" (very small/thin printed circuit board) by using the smallest SMD transistors available today VML0806 package?How far can a hobbyist create their own miniature transistor based electronics? And you have to be good in designing circuits with the least possible miniature components. (without expensive industrial equipement)https://duino4projects.com/wp-content/uploads/2015/02/Rohm-claims-to-have-smallest-transistor-package.jpg

author: Kleinstein
author_rank: Super Contributor
timestamp: April 28, 2022, 08:46:31 pm
content: Even with small SMD types a circuit can fast get quite large. There are a few cases where discrete transitors may replace an OP or 2, but this often comes at the cost of high power consumption and size. More normal OP's are still available and it would be mainly more special cases (e.g. > 40 V) where on may consider a dicrete build version. Similar one may go back to JFET switching instead of CMOS switches in some cases.Another problem with a discrete build solution is that it usually more time to design and not many are used to such types of designs.To allow debugging the first iteration tends to be relatively large to have extra space for probes and bodges / resistor changes.Discrete parts are also a bit limited when it comes to small, low capacitance transistors.

author: jwet
author_rank: Frequent Contributor
timestamp: April 29, 2022, 04:47:46 pm
content: It's "possible" but not especially practical.Checkout the "https://monster6502.com/"- a 6502 CPU made discretely- only 12x15" and a lot of time. By Eric Schlaepfer- he estimates cost at about $3k, mostly labor.

author: Sredni
author_rank: Frequent Contributor
timestamp: April 29, 2022, 09:12:19 pm
content: well, for hobbyist purposes only, I find it oddly satisfying to use discrete multivibrators, essential comparators, and small op amps (basically a differential amplifier with a buffer stage, and if I am in the mood a current source for biasing) to do very basic stuff. Not because I need, but only because I can.Seeing the multivibrator working with a 0.7 volts supply was... nice. Try to do that with a 555 or a microcontroller.But for practical purposes... ICs are much more robust. One would need a lot of discrete transistor to add all the functionality we take for granted.A link to a site that offers discrete op amps:http://www.nanovolt.ch/resources/discrete_opamps/index.html

author: John B
author_rank: Frequent Contributor
timestamp: April 29, 2022, 09:20:35 pm
content: It sounds like a nightmare cycle of committing to a design, getting the PCB, assembling the board, then wanting to tweak something small to change a minor aspect of the functionality, then back to step one....

author: jwet
author_rank: Frequent Contributor
timestamp: April 30, 2022, 12:44:48 am
content: Imagine committing to launching an IC into a fab. The cost to make a set of masks for a modern IC is unbelievable (millions) but committing any IC to a fab is big gamble. Lots and lots of simulation is the standard answer but not everything shows up. Committing to a PCB is nothing in comparison.

author: Someone
author_rank: Super Contributor
timestamp: April 30, 2022, 01:11:25 am
content: Start by finding the actually smallest package. I'll drop the bar a little lower:XDFN3 0.42x0.62mmAdd in some embedded and/or printed in PCB components and you're getting there.But how granular do you need to go? Many digital logic, opamps, and comparators (much larger functional blocks) are already multi sourced and or interchangeable with other model numbers. Engineering, balancing n different competing priorities.

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 30, 2022, 01:57:30 am
content: Many things can't be efficiently implemented with discrete transistors.For instance, most discrete MOSFETs (but a few exceptions) available do have their source and bulk internally connected. That causes issues for implementing a lot of stuff.

author: Sredni
author_rank: Frequent Contributor
timestamp: April 30, 2022, 02:28:56 am
content: Also current mirrors are a pain to implement with discrete transistors. One needs to do a bit of selection to get the best matching. On a die, the matching is a direct consequence of being created there.