We found this circuit that can reach 50 MHz in the February 1997 Electronics Now magazine. The integrated circuits used are not very common today.
This circuit from a Popular Electronics from the 90's can generate signals from 0.03 Hz to 3 kHz...
The presented circuit provides an output voltage proportional to the input current, according to...
The 4528 is a dual-retriggerable monostable that needs only the timing network formed by R and C...