Art of Electronics 3rd ed. Figure 2.32
Left:
Load is the collector resistor (NPN current sink)
Stiff (R1||R2<<βRe) voltage divider gives Ve≈1V emitter voltage, which creates Ic≈Ve/Re≈1mA current
Middle:
Load is the collector resistor (NPN current sink)
Zener diode gives a reference voltage of Vbe=5.6V which gives Ve≈Vb-0.6V≈5V.
Ic≈Ve/Re≈0.5mA
Right:
Load is the emitter resistor (PNP current source)
Three diode drops creates Vb≈10-1.8≈8.2V
Vc≈Vb+0.6V≈8.8V (PNP)
Ie≈(10-Vc)/Rc=1.2/560≈2mA
