[sdiy] only the highest voltage may pass

[asfi at eol.ca]

Quoting Dave Krooshof <synthos at xs4all.nl>:

> I was wondering...
> 
> Do analogue OR ports exist?
> In the digital domain (MaxMSP) I use an object that only passes the
> highest of 2 inputs. You can make very interesting LFO shapes with it.
> 
> So I hope there's a IC that does just that:
> pass the highest of 2 input voltages and ignore the lowest input voltage.
> 
> And oh yeah, If they come with 4 in a IC, I'd be really happy.
> (I like complex behaviour in electronics). I googled on analoge OR
> and things like that, but not with any succes.

Well, I'll admit that I know beans about analogue circuit design,
compared to some of the real wizards here, but I can't help but
answer.....

If the signal is unipolar (i.e. you only need a positive maximum of
two positive voltages, and don't need the negative | maximum
amplitude | of two negative voltages) then it should be pretty simple.

Use diodes. You'll likely want to compensate for the offset introduced
by the voltage drop across the diodes, but that's not difficult unless
you need precision.

- Colin Hinz
  Toronto, Canada