Saw/triangle wave generator schematics?

[Dr. K]

I've been playing around with a "ring mod" (I realize it's not a true ring mod) from a 4093 quad NAND gate. I am using square waves from a 40106. Really simple at the moment.

I was thinking the other day, it would be fun to feed it from some kind of "siren"--I could use the CV input on a 555/556, and feed it triangle or saw tooth wave.

Does anyone have an easy triangle/saw wave schematic? Ideally something you could adjust from a steep leading edge, through a triangle wave, to a steep falling edge? I'm not super familiar with this, but it seems like it should be possible using diodes and a voltage divider in a feedback loop?

Thanks for any info--I've been googling the heck out of it this morning and not coming up with much!

[PHOBoS]

if you want to keep it really simple you should be able to get something like that with 2 diodes a pot and a capacitor
connected to the output of a squarewave oscillator:
- connect the anode of diode 1 to the osc. and the cathode to an outer lug of the pot.
- connect the cathode of diode 2 to the osc. and the anode to the other outer lug of the pot.
- connect the capacitor between the wiper of the pot and GND.
The voltage over the capacitor will be your CV signal.

note that both the amplitude and waveshape will vary depending on the oscillator frequency, but for something like this
it might give interesting results.

[Dr. K]

I'm going to breadboard that this afternoon. I read up a bit on those systems, and it seems pretty straight forward.

I'm wondering about something else. I recently built a dub sired based on the attached schematic. The first 555 is just a triangle wave generator that feeds the CV of the second. What I'm not sure about is the purpose of the op-amp stage in between.

If the circuit idea you provided works out--and generates an adjustable saw/triangle wave form, would it require a similar op-amp stage? I'm not certain why it is included. Without anything in the feedback loop, it should have 0-gain, shouldn't it? It's a buffer of some kind?

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[Grumble]

[Grumble]

I’ve found a datasheet from Intersil HERE, where the value is given of the 3 resistors at the control voltage input, being about 100k typical so a total of 33.3k which is better but not high enough to remove the opamp buffer.