An Alternative XR Triangle Wave Method

[Thomas Henry]

The VCO Chip Cookbook (now in print) took nearly three years to write. Naturally, after it was all done and on the way to be published, I discovered a few other things I could have included. I've decided to attach them here as freebies for readers as I get time to do so. You might want to print them out and paste or staple them in your copy of the book for reference; that's what I'm going to do with mine.

So, the first one is a slick alternative to the triangle circuit on page 87 (figure 77). What makes this so neat is that the triangle is in-phase with the square wave. Moreover, using the non-inverting input of the op-amp ensures there is no loading to corrupt the triangle. Finally, there are trimmers to adjust both the center and the amplitude of the triangle precisely if that's important to you.

It might not seem like much, but this really worked out nicely to give a perfect +/-5V, in-phase triangle. I've labeled the sheet Figure 77(b), but it should also be useful with the Triangle/Ramp Switch of Section 35, and the Ramp Wave by Multiplication method of Section 36.

More to come later...

Thomas Henry

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[Scott Stites]

Pretty interesting. I never looked at the phase relationship between the pulse and tri/ramp of the XR VCO - how do they compare?

Cheers,
Scott

[goodrevdoc]

Cool thanks, I'll have to make some breadboard real estate!
-justin

[Thomas Henry]

Oops...I was just winding down for the night, and noticed that the line to the buffer input got messed up on the schem.

I've fixed it and posted the updated version in its place. If you've already downloaded the schem, do so again and discard the old one.

I might mention that this happened after only two pints of Guinness; I must be getting feeble...

Thomas Henry

[State Machine]

Thanks Tom, I will send a copy of this added figure with the books that I sell.

Bill