Another solution to generate rectangular signals of some hertz up to 5 MHz is the one that makes use of two CMOS inverters, as shown in figure 1.
This RC oscillator has its frequency calculated exactly by the first formula where Vtr is the trip voltage of each port. A simpler formula, which disregards this factor, since it is approximately the same for a wide range of feeds, is given below, in the diagram itself.
The resistor Ra must be at least 10 times greater than R. Typical values of R are in the range of 10 k ohm to 100 k ohm and the capacitor between 100 pF and 100 nF. The generated signal is rectangular. Any CMOS function that can be configured as an inverter can be used in this oscillator, such as NOR, NAND, Inverter, etc. ports.
In figure 2 we have a suggestion of printed circuit board for implementation of this oscillator.
Material list
CI-1 - 4011, 4001 or other CMOS inverter - see text
Ra - 100 k ohm - see text
R - 10 k ohm - see text
C-10 nF to 100 nF - capacitor
Several:
Printed circuit board, wires, solder. etc.
