LM3900-Fu

fadeddata · Joined: Dec 27, 2004 Posts: 43 Location: Nashville TN

Hello All,

Maybe this can start a general thread about the LM3900 and it's seemingly endless uses regarding audio. I was curious if anyone out there can explain the Trigger Input and the End Out of the CGS75 VCs.

I've been breadboarding the circuit over the last few weeks and have had trouble getting these sections to work.

The reason I didn't put this in the CGS thread is I was also interested in seeing what other good uses the LM3900 can be put to.

-dustin

fadeddata · Joined: Dec 27, 2004 Posts: 43 Location: Nashville TN

Here is one reference I've been returning to over and over again.

http://www.national.com/an/AN/AN-72.pdf

I think I'm now starting to grok some of the introduction.

-dustin

Tim Servo · Posted: Wed Sep 30, 2009 3:37 pm Post subject:

For some lo-fi (but fun) 3900 circuits, dig up the schematics to the old PAiA Gnome. I'm pretty sure a PDF of the original magazine article can be found out there. John Simonton managed to get a linear VCO, VCF, VCA and a couple of simple envelope gens out of one 3900 (and a bunch of transistors).

Tim (medium-fi) Servo

andrewF · Posted: Wed Sep 30, 2009 7:07 pm Post subject:

It seems Serge was quite fond of the LM3900, the negative slew, positive slew and EG all had them.
As did the original Serge oscillator

fadeddata · Joined: Dec 27, 2004 Posts: 43 Location: Nashville TN

Excellent links! I didn't know the Gnome used an LM3900. I'm going to dig into the Negative & Positive Slew to see if I can make out how the End Out works on the VCs, quite the long shot Smile

-dustin

uniqview · Posted: Sat Jan 20, 2024 1:14 am Post subject:

I'm very late to this party, but I have a blog which is about the title of this thread:
https://beyondan72.blogspot.com/