We found this circuit in a Poptronics from 1998. The circuit can be extended to more competitors with another 4011. The power can be made with voltages from 6 to 12 V.
This circuit uses a voltage comparator and can produce signals up to 20 MHz. The resistors R are...
It can be obtained from Mouser Electronics the new LM290xAQ operational amplifiers from Diodes...
This circuit was obtained from a Texas Instruments 1985 document. The circuit is powered by 1.5 V...