Yes, Toba was a big one left a crater 18 miles by 65 miles. Scientists think humans were reduced to 5 to 10 thousand individuals based on the DNA studies. Yellowstone has had 3 big ones and we are about due again. The last one was not the biggest. My father wrote a novel about the next big one which some day I may rework into a publishable form.
That sounds like it would be an interesting read! The whole idea is fascinating, and terrifying at the same time.