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OErjan
 Post subject: sawtooth circuit wanted
PostPosted: Fri Dec 18, 2009 10:09 pm 
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Joined: Sun Nov 12, 2006 6:09 pm
Posts: 1304
Location: N 64º 41' E 21º 14'
As subject state.
I need a 150khz+ (500 would be a dream) sawtooth into a mixer, preferably with 5V high peaks and "flat" flanks and quick drop, I have found several using opamps and ujt also "simulated ujt" (PNP and NPN transistor as a twisted darlington) but all seem to fail my wishes.

the 555 starts to fade out around 15kHz by the way out of 7 circuits tested (not counting number of swapped resisors/caps) best was 18.3kHz.

the ones in links below I have not been able to push high enough in frequency or get working at all on my breadboard.
http://www.vk2zay.net/article/196
http://homepages.internet.lu/absolute3/ ... zdiscr.htm
what am i doing wrong? that last should work but...
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XtalHWJ
 Post subject:
PostPosted: Sat Dec 19, 2009 1:47 am 
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Joined: Thu Mar 12, 2009 4:09 pm
Posts: 923
Location: Sonoma County, CA
I have used the CMOS version of 555 above 200 KHz.

Rich

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Homebrew Radio ex-Silicon Valley
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OErjan
 Post subject:
PostPosted: Sat Dec 19, 2009 11:14 am 
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Joined: Sun Nov 12, 2006 6:09 pm
Posts: 1304
Location: N 64º 41' E 21º 14'
YAY, the cmos 555 apparently works up to 1300kHz, thank you, have ordered 2, now all i need is something to get me by over cristmas.
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foolsgolden
 Post subject:
PostPosted: Sun Dec 20, 2009 4:34 pm 
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Joined: Wed Dec 17, 2008 3:49 pm
Posts: 706
Location: new jersey
Quote:
i need is something to get me by over cristmas.


does this help?


i am pretty shore its a cheesy schematic from a radio shaft science project toy but merry Christmas :D Image

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31 years old now playing with crystal sets since 12 years old tweaking and tinkering and sharing ideas ever since...Image
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OErjan
 Post subject:
PostPosted: Mon Dec 21, 2009 9:08 pm 
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Joined: Sun Nov 12, 2006 6:09 pm
Posts: 1304
Location: N 64º 41' E 21º 14'
it si worth a try, i have tried something like 20 different circuits and yet none is quite enough.
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Georg
 Post subject:
PostPosted: Mon Dec 21, 2009 9:16 pm 
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Joined: Sat Oct 13, 2007 1:46 pm
Posts: 359
Hello Oerjan,
look into this paper:
http://www.exar.com/Common/Content/Prod ... ?ID=XR2206
Regards
Georg
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OErjan
 Post subject:
PostPosted: Mon Dec 21, 2009 9:38 pm 
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Joined: Sun Nov 12, 2006 6:09 pm
Posts: 1304
Location: N 64º 41' E 21º 14'
i have a MAX chip on its way together with the 555, the MAX chip is similar to what you posted Georg
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golfguru
 Post subject:
PostPosted: Mon Dec 21, 2009 9:48 pm 
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Joined: Sat Aug 18, 2007 8:52 pm
Posts: 1996
Location: Australia
1MHz maximum.
http://cgi.ebay.com.au/XR2206-XR2206CP- ... 2556494873
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