# What is the difference between “Collector-Emitter” and “Base-Emitter” Saturation Voltage?

As you can see on the datasheet below for the 2n2222a NPN transistor, the "Collector-Emitter Saturation Voltage" and "Base-Emitter Saturation Voltage" are defined respectively as 0.3 to 1.0 and 1.2 to 2.0. I believe I understand transistor saturation, but whats the difference between Collector-Emitter Saturation and Base-Emitter Saturation?

Vce(sat) is the voltage measured at the collector relative to the emitter under the specified conditions (say 150mA of collector current flowing, and 15mA of base current applied (forced beta of 10).

Vbe(sat) is the voltage measured at the base relative to the emitter under the specified conditions, as above.

So if you are wanting to switch a 150mA load under those conditions with (say) a 10V input, you will use the latter number to determine the required resistor value to get the minimum base current needed (and ensure you don't exceed any maximum if the minimum Vbe(sat) is specified).

What's the difference between Vbe(sat) and Vce(sat) ?