This relaxation oscillator circuit consists of two bilateral switches of CD4066 integrated circuit (see the figure below). The first switch DD1.1 works as a non-inverting Schmitt trigger, the second one switch DD1.2 works as an inverting circuit.
DD1 - 1/2 CD4066; C1 - 1 nF; R1 - 20 kΩ;
R2 - 100 kΩ; R3 - 600 kΩ; R4, R5 - 4.7 kΩ
Resistors R2, R3 are determined the hysteresis of the Schmitt trigger. The output frequency of the relaxation oscillator depends on parameters of the network R1C1 and the hysteresis value. The output impedance of the circuit is determined by the value of the resistor R5 and the resistance of the bilateral switch DD1.2.
The circuit works with the power supply voltage of 3..15 Volts. The pin 7 (Low Voltage Power Pin) of the DD1 should be connected to the ground wire, the pin 14 (Power Pin) should be connected to the power supply voltage.
The LTSpice model of the relaxation oscillator circuit can be downloaded from here: the_relaxation_oscillator_circuit_with_cmos_ic_cd4066.asc. The simulation required the CD4000 library: CD4000.