I don't think the dollar fits the definition of a ponzi scheme.
"An investment swindle in which some early investors are paid off with money put up by later ones in order to encourage more and bigger risks" - Merriam Webster Dictionary
By this definition, most of the large economy activities are ponzi schemes, like pension plan, housing, government bonds etc...
Currently the biggest ponzi scheme is the government bonds investment, of course they don't need later ones to support the early investors, they just need to print more money and sell more debt exponentially to financial the previous debt