Crazy questions corner !

[ivconic]

While reading Carl's post #2 on the topic "Optimum component selection"... a "crazy" idea came to me completely randomly!
One of the most important properties of the FET transistor in the PI detector is the resistance in the "On" state.
Has anyone ever thought of two (or more) parallel fet transistors in a PI TX stage?
A parallel connection will affect the resistance but also the maximum current that can pass through such a parallel connection, right?
In order for parallel fets to work identically; I believe that it is not easy to "match" any two fet even from the same series.
Some subtle differences will always exist.
But I also believe there are specially packaged multiple fet with fairly uniform characteristics.
Crazy idea, right?

[Carl-NC]

Minelab did this in the SD2000, probably others.

[ivconic]

Really!?
I've had the SD2000 schematic for years and never looked at it.
So much for how interested I was in the past.
I wouldn't be interested even now... but for the last few years the topic of PI detectors has been predominant on the forum.
Nobody is talking about anything else.
...
Ok, why is such a solution not generally present in the countless PI projects we have on the forum?
What are the disadvantages? What is it that deters people from exploiting such a solution?

[Carl-NC]

The SD2000 was released in 1995, now almost 30 years ago. Back then the selection of MOSFETs was far more limited so ML probably paralleled them to get a decently low rds (turn-on R is more critical for them). Now, electric motor apps have greatly expanded the selection of MOSFETs so it's easy to find the right rds and even with a low Cds. And paralleling FETs doubles the capacitance.

[ivconic]

Yes, of course. I forget easily, I remember hard.
Thanks!
...
I'm just reading some old posts on the subject of QED.
Finding some of my posts??
I don't believe that I wrote that and that I even participated in that topic!???

[ivconic]

Ok Carl!
How about this crazy thing!
"Poor man" high precision pulse generator!
8-10mA.
How about this clocking the PI TX ... or VLF I/B ?

[Carl-NC]

Sure, that will work. I'm not sure how stable the 4066 turn-on threshold is. Personally, I would just use an 8-pin micro. BTW, the lower 5V swing is actually 9V.

[ivconic]

Not that it's hard for me to write simple code for Attiny to do the same (and much more)... but this is so crazy and unusual that I couldn't resist!

[ivconic]

How about walking on a wild side?
It's always a problem to easily find a quality component, especially if the budget is limited or you live far from modern trends...
A good opamp is always hard to come by in such conditions.
Especially if you need single supply, rail to rail! A rarity in my world!
And then you discover and find it very easily and the price is ridiculous!
MAX4466!
https://vi.aliexpress.com/item/10050...Cquery_from%3A