RE: Schmitt trigger for feedback SSTCs

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Original poster: "Steven Ward" <srward16-at-hotmail-dot-com> 

Hi Greg,

Hmmm, seems there might be 2 problems with using a 555 as a schmitt 
trigger.  1, the input impedance might be too low (if you want to feed an 
antenna into it or similar) and 2, might be too slow (not sure what the 
propogation delays would be on that circuit).  But the best way to find out 
is to build it!  I do like the idea of eliminating the 5V supply ;-)

Steve


>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Schmitt trigger for feedback SSTCs
>Date: Thu, 29 Apr 2004 08:56:26 -0600
>
>Original poster: Mr Gregory Peters <s371034-at-student.uq.edu.au>
>
>Hello all,
>
>Been looking at common, cheap schmitt triggers used for feedback SSTCs, 
>and have noted that they:
>
>a) generally only run on 5v
>
>b) Can only supply a few tens of mA output
>
>
>Anyway I found this circuit at:
>
>http://www.uoguelph.ca/~antoon/gadgets/555/555.html
>
>Go to the "example circuits" section, figure 9.
>
>It is a 555 timer being used as a schmitt trigger to clean up dirty wave 
>inputs. Seems this would be useful to us SSTCers, as it is cheap, can run 
>off 12v, and can supply up to 200mA output current.
>
>Is there any reason why this couldn't be used in a feedback SSTC system?
>
>
>Cheers,
>
>Greg Peters
>Department of Earth Sciences,
>University of Queensland, Australia
>Phone: 0402 841 677
>http://www.geocities-dot-com/gregjpeters
>