[sdiy] Triangle-to-saw conversion

[Tim Parkhurst]

On Tue, Feb 16, 2010 at 8:47 PM, Aaron Lanterman
<lanterma at ece.gatech.edu> wrote:
> Is there a "canonical" example of triangle-to-saw conversion?
>
> Saw-to-triangle is pretty easy to explain, but the other way around is trickier.
>
> - Aaron
> ____

Hi Aaron,

Although I've seen some minor variations, the way to go is to use a
"sign changer" op-amp configuration controlled by an FET or analog
switch. You use the square wave from the triangle core to alternate
between inverted and non-inverted versions of the triangle. If you
offset the triangle just the right amount, the inverting and
non-inverting slopes align and you get a nice smooth ramp (if the
offset isn't right, you get a slight discontinuity in the ramp). So,
with one op-amp for the offset, and one op-amp and an FET for the sign
changer, you're all ready to go. BTW, this only works because the
triangle and square are 90° apart in a standard tri core oscillator. I
first saw this method used in the Thomas Henry LM VCO, and I've used
it in a few different Magic Smoke products. I'll send you a schemo if
you'd like. Let me know.


Tim (have a discontinuity in my ramp, but I wear long pants so it
doesn't show) Servo
-- 
"Sire, the church of God is an anvil that has worn out many hammers."
- H.L. Hastings