# Applying +U & -U to BJT Load Line

So, I was wondering, how to draw or specify Vcc to the output characteristic (Ic versus Uce - common emitter), when we apply positive voltage (+12V lets say) to the collector and negative voltage (-12V) on the emitter terminal.

Should Vcc value (to be used in calculations) be 12V or 24V? When calculating Rc = Ucc/Isat , which of two values should be used?

Is there anything special about this circuit (when we talk about biasing of the transistor with two power supplies - one positive & one negative)? Is base still biased to approximately 0.7V?

• What you have drawn with the batteries in series produces exactly zero volts to the transistor. Also, have you ever heard of a negative voltage battery? Use 24 volts. – Andy aka May 22 '17 at 14:44
• @Andyaka I am just curious if the Ucc here represents 24 Volts? So output signal can vary from -12V to +12V? – Keno May 22 '17 at 15:17
• Note the x-axis is Vce, so you can use the standard I-V characteristics of an NPN transistor. – sstobbe May 22 '17 at 15:24