Bi-pulse convertor (ON-topic)

[danial stocks]

This is basically a pulse wave
> > where the positive and negative halves are generated separately and work 
>in
> > opposition. The top varies from 50% to 1% while the bottom varies from 
>50%
> > to 99%, and vice versa.
> >
> > The waveforms (converting from a ramp) look something like this:
> >
> > 0% CV
> >
> > ----------              +5
> >           |
> >           |
> >           |              G
> >           |
> >           |
> >            ----------   -5
> >
> > 50% CV
> >
> > -----                   +5
> >      |
> >      |
> >       ---------          G
> >                |
> >                |
> >                 -----   -5
> >
> > 75% CV
> >
> > ---                     +5
> >    |
> >    |
> >     -------------        G
> >                  |
> >                  |
> >                   ---   -5
> >
> > Sounds like PWM but distinctly different. Should also work with a 
>triangle
> > input. Obviously this is a simple quantization problem, which has been
> > discussed before. Anyone have a schematic?
>
>Nope, but let's make one... this is done by using three op-amps and
>four resistors...
>
>                           |\
>                       +---|+\    ___
>  CV ------------------|-+ |  >--|___|-+
>          ___     ___  | *-|-/    1k   |
>      +--|___|-*-|___|-* | |/          |
>      |   10k  |  10k  | |             *---- Out
>      |        |  |\   | | |\          |
>      |        +--|-\  | +-|+\    ___  |
>Saw -*           |  >-+   |  >--|___|-+
>      |        <|-|+/    +-|-/    1k
>      |           |/     | |/
>      +------------------+
>
>That ougth to do it. Throw in buffers as required.
looks good but I'd add in inverse parallel diode clippers after the 1k res, 
then mix in an op amp summing stage... this circuit is making the assumption 
that the + clip on the op amp occours at the same level as the - clip.. and 
this is not always the case [LM324.. etc ..] also probs with phase 
inversion? OTOH a comparators should work well here, but the o/p res should 
be high to the op amp in mix,... also, feeding with a triangle wave will 
give interesting other waveform..

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Cheers,
Dan
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