The third option, Chipdraw, also provides free hand drawing but this time starts with a square wave. The oscillator design is 4-bit and this is indicated by the stepped behaviour as you begin to draw.

A symmetric and accurate triangular waveform generating circuit is described. A simple approach in maintaining the symmetry and linearity of triangular waveform is made by using a single constant ...

The operation and performance of a new type of circuit for square-wave generation is presented. The circuit is based on the application of two identical regenerative switches using complementary ...