This circuit is based on the voltage drop of the diodes in conduction, in the order of 1.6 to 1.7 V. The current is very low and the input can be in the indicated voltage range.

This circuit is based on the voltage drop of the diodes in conduction, in the order of 1.6 to 1.7 V. The current is very low and the input can be in the indicated voltage range.