# Does it make sense to plot resistor current vs input voltage in this circuit? simulate this circuit – Schematic created using CircuitLab

I'm a bit confused by a question which asks me to plot current through R1 as a function of Vin using a constant voltage model for D1. I'm a bit confused by this. Given the model, even if I considered Vin to be the voltage over the current source, wouldn't it be V_Diode_on once I_in*R1 = V_Diode_on? Does this make sense or is this likely a typo and I should be plotting V_R1 as a function of I_in?

• But if Vin's voltage doesn't go higher than that ... do I just stop the graph at Iin*R1 = V_diode_on? Oct 2 '15 at 4:05
• But that doesn't make sense does it? There is no value of i_R1 for Vin > V_diode_on because there is no voltage higher than V_diode_on? Am I making sense? Oct 2 '15 at 4:07
• That doesn't make sense ... there's voltage higher than V_diode_on from the current source when v_out can never be higher than v_diode_on? I get that increasing current from the source would only increase diode current, but I don't see how the input voltage could change without the output voltage changing. Oct 2 '15 at 4:12
• I agree with you - it's a typos and should say Iin. Oct 2 '15 at 4:15