# NPN Switch when ON operating in Forward Active or Saturation Region?

When an NPN transistor is used as a switch as shown below, is it operating in the Forward Active Region or the Saturation region when it is turned ON? I believe its working in the Forward Active Region since V_BC = 0V < 0.4V and V_BE = 0.7V. I read somewhere that an NPN is in saturation when operated as a switch in the shown configuration. I'd appreciate if someone can clarify.

• $V_{CE}$ when the transistor is on will indicate if it is in saturation. In your case $V_{CE} = 0.7~V$ and therfore not in saturation. – skvery Feb 26 '17 at 20:46
• @skvery how do you know V_CE=0.7 V? – athedcha Feb 26 '17 at 20:55
• $V_{BC} = 0~V$ – skvery Feb 26 '17 at 20:57
• Saturation is a property of a circuit, not a property of a transistor in isolation. When $\vert V_{CE}\vert \lt \vert V_{BE}\vert$ then the transistor is moving into saturation. – jonk Feb 26 '17 at 20:57
• Use a multimeter to measure the voltage from emitter to collector when your CONTROL input is at 5V. If the measured voltage is less than say about 0.5V then the transistor is for sure saturated. – Michael Karas Feb 26 '17 at 20:57