The oscillator shown in figure 1 uses one of the four comparators of the LM339 integrated circuit.
The frequency is 100 kHz but close values up to 1 MHz can be obtained with other crystals. The power supply can be made with voltages from 5 to 12 V and the output is rectangular.
The other three comparators of the same integrated circuit can be used in other functions, since they are completely independent. In figure 2 we have a printed circuit board taking advantage of the first of the comparators. Around the others the developer can elaborate other oscillators or other functions.
Material list
CI-1 - LM339 - Quad Voltage Comparator
R1, R2 - 220 k ohm x 1/8 W - resistors
R3 - 100 k ohm x 1/8 W - resistor
R4 - 2.2 k ohm x 1/8 W - resistor
XTAL - 100 kHz crystal
C1 - 100 nF - ceramic capacitor
Several:
Simple power supply, printed circuit board, wires, solder, etc.
