Low-cost generators are implemented with analog circuits that feature continuously variable frequency and output voltage.

The AG52 analog signal generator offers fast rise time square waves, lower noise floor and more for APx audio analyzers.

This circuit and its description can be found as figure 13 in the AD8037 data sheet. (from the days when ADI appended lots of lovely app notes). The second pulse generator output (left) can be found ...

I realise diamond buffers have their limitations, but at least they are fast (in modest rf terms) and have good driving capability. All the transistors are on all the time, so there are no delays ...