While I was designing a constant current source using a 2N3904 I noticed a behavior on the bjt that prompted me to look closer into it.
The issue is that although the datasheet specifies a minimum BVceo = 40V. Any voltage above 8VDC on the collector with base either floating or grounded (as shown on schematic) creates an sudden increase in collector current (suggesting breakdown) and the voltage across C-E is decreased as to limit power across C-E. I breadboarded the circuit below to investigate this.
My current mirror is to be used on the output stage of an audio headphone amplifier with Vcc = 12V. Any help understanding this would be greatly appreciated.