Suppose that the bias circuit used to generate Fig. 20.16 shows a reference current change with VDD, as seen in Fig XXXXXXXXXXKnowing that the reference current should be constant with changes in VDD,...

Suppose that the bias circuit used to generate Fig. 20.16 shows a reference current change with VDD, as seen in Fig. 20.54. Knowing that the reference current should be constant with changes in VDD, what is wrong with the reference? (What important portion of the reference is causing the problem?)