electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
go to the radio page Live at electro-music.com radio 1 Please visit the chat
poster
 Forum index » DIY Hardware and Software
Sawtooth VCO - help!!!
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 3 of 3 [52 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Goto page: Previous 1, 2, 3
Author Message
frijitz



Joined: May 04, 2007
Posts: 1734
Location: NM USA
Audio files: 54

PostPosted: Sun Jan 05, 2014 4:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

synchroma wrote:
But, at the moment of discharge in Bernie Hutchins' design, "the capacitor voltage is +20 volts (-15 from the comparator, and +5 fed in from the ramp through R12)" (page 2, paragraph 3 from http://www.synthsource.com/ens76/vco2.htm).

That's the voltage across C4, not the integrator cap!
Quote:
Therefore the voltage at the Drain of the JFET is positive +20V relative to the voltage at the Source +5V at the moment of discharge.

No, the voltage at the drain is +5V and the voltage at the source is 0V.

Quote:
As an experiment I tried swapping around the MOSFET I'm using in my own design, connected with the Drain at the input from the Exponential converter. It's an enhancement mode N-Channel MOSFET (2N7000). When I put it the other way around, the circuit stopped working. Of course the gate in my circuit goes from 0V to +15V, rather than -15V to 0V.

MOSFETs are different from JFETs. For a good MOSFET-based design see this old thread:
http://electro-music.com/forum/topic-28713.html&postorder=asc&highlight=mosfet+ian+vco&start=25

Ian
Back to top
View user's profile Send private message
synchroma



Joined: Oct 18, 2011
Posts: 72
Location: London
Audio files: 2

PostPosted: Sun Jan 05, 2014 5:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Oh, I goofed in reading that, and yes it is C4, but Drain is still positive relative to source. Intuitively I think the JFET should conduct in both directions from reading some theory about it, but I just never got it to work the other way around.

Anyhow, I've found some methods that work for me. Thanks for the link to MOSFET designs Smile and thanks generally ian for your help.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 3 of 3 [52 Posts]
View unread posts
View new posts in the last week
Goto page: Previous 1, 2, 3
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use