[sdiy] Saw core JFET mystery

[Magnus Danielson]

Aaron Lanterman wrote:
> On Mar 1, 2010, at 8:11 PM, David G. Dixon wrote:
> 
>>> Yep, that looks pretty much like mine, albeit with different component
>>> values...
>> except for that transistor on the end of the comparator.  What's up with
>> that, Magnus?
> 
> Danger Will Robinson!
> 
> I had a student build this a couple of years ago:
> 
> http://home.swipnet.se/cfmd/synths/friends/stopp/asm1vco-1.1.pdf
> 
> and it turned into an absolute nightmare because of the confusion that transistor caused. It worked muh better once we knew to not include an actual transistor there.
> 
> That transistor is *part of the LM311* - it's trying to illustrate the open collector output of the 311. 

Correct. I was trying to illustrate that this is not just a normal 
op-amp. I forgot to draw a box around the compound.

> Repeat, repeat, *don't* put a transistor in that spot - just hook the output of the 311 to the node connected to the collector of the phantom transistor.

Or rather, do put the transistor there... along with the rest of the 
LM311 you put there, but do not put in an extra transistor.

This is the first time I can recall that this little drawing-aspect 
causes troubles. I also don't recall anyone asking about it.

Could people stop linking to the OLD++++ site at SWIPNET? NOW.

Cheers,
Magnus