This is a very common signal diode – 1N4148. Use this for signals up to 200mA of current. Very general purpose, it’s got a typical forward voltage drop of 0.72V and a 300mA maximum forward current rating.

The voltage drop accross a diode is a non-linear function of current. It is not a fixed voltage source, but is around 600-700 mV for most normal currents.

A regular 1N4148 silicon diode has a forward drop of about 0.65V, quite a bit when supplies are 2..3V!

The Schottky diode has a much lower voltage drop. It’s usually specified as 0.3..0.4V, but it really depends on the amount of current passed through it.