Heidi
Member
Dear friends,
In the figure above, V_BE indicates the Base-Emitter voltage.
In my text, it says "the effect of V_BE “uncertainty” becomes more pronounced at low values of VCC because (VCC - V_BE) determines the base current. Thus, in low-voltage design, the bias is more sensitive to V_BE variations among transistors or with temperature."
I have a few questions about those statements. First, what does it mean by 'the effect of V_BE “uncertainty” becomes more pronounced at low values of VCC?' Is 'V_BE uncertainty' saying that V_BE won't be exactly the same even when transistor Q1 is replaced by another identical one?
Second, I can see that I_B = (VCC - V_BE) / R_B, referring to Figure 5.15 above, once we can be sure about the value V_BE, we know what the base current will be. What does it mean to say "in low-voltage design, the bias is more sensitive to V_BE variations among transistors?"
Thank you!