[sdiy] TZ triangle core

[Neil Johnson]

Hi Ian,

> Turns out it doesn't. The reason is that it only will work with one  
> input polarity.  The opposite polarity puts the integrator/ST out  
> of phase, so the system runs immediately to the rail.  <headslap>

Yes, 5 minutes thinking about this and I come to same conclusion:  
once the Schmitt has reversed the signal trajectory it won't flip  
until the other bound is reached.  If the signal reverses due to  
external control then the Schmitt won't see it as its looking in the  
wrong direction.

So a window comparator is needed, coupled to a T-flip flip as you  
say.  This should catch the signal whatever bound it reaches,  
irrespective of its history, and then flip its direction.  I would  
also add a safety window comparator set to wider limits (say +/- 7V)  
to catch any unfortunate startup conditions.

Cheers,
Neil
--
http://www.njohnson.co.uk