Single/Dual-Supply Comparator / Operational Amplifier - RC Astable Multivibrator

This is a nonlinear, RC relaxation oscillator using a comparator or an operational amplifier, the circuit is configurable for single or dual supply operation. Essentially only the voltage levels of the waveform are different in single and dual power supply modes. Charge and discharge times are the same in single and dual supply modes; consequently, the period/frequency is the same in two modes. When using a comparator, the circuit shown is for push-pull output drivers. For open-collector/drain output comparators a pull-up resistor from the output to the positive supply is needed. The pull-up resistor provides the charging path for the capacitor. If differences in timing relative to the circuit shown is to be minimized, the pull-up resistor should be as low as possible.