Recently, I was looking thru YouTube and came across a sawtooth generstor on chan w2aew vidieo no.104 Aug 2013. I thought it was interesting enough to try out on the EC simulator. Some important notes.
1. The relay in the EC simulation is not required in the actual hardware. It is being used to isolate the output of the comparator from the other active devices in the overall feedback loop. Without the relay isolation, EC will stop with a convergence error (No Solution Found). I have encountered this problem before with EC whenever I try to add active devices as part of the feedback loop of the OA. I suspect it's the result of the EC implementation tradeoff made between an easy to use GUI or adding Spice simulation complexity.
2. Although the configuration of the 4 diodes in the center may not be easily recognized, they are just configured as a standard full wave bridge being used as diode switches.
3. In the actual hardware, remove the relay and all it's connections and connect the output of the comparator directly to the pn junction of the left set of diodes. A high at this control point will switch in the current source (ramp up - charge cap) while a low will switch in the current sink (ramp down - discharge cap). The sawtooth symmetry can be adjusted by changing the source and sink currents. Frequency is most eaisly changed via the capacitor at the bridge output.
4. For a more complete explanation of the circuit, see the YouTube video mentioned at the beginning.
