this is a feedback loop. M38 and m39 are connected to ensure a negative feedback loop. This is why this scheme is stable. Without M38 you dont have a current source.
I find such kind of CMOS current source is very stable
and it is also very robust to the process and temperature variations
From my understanding, transístor MN39 itself and the resistor R14 can already determine the current, why do we still need another transistor MN38 in this case?
wondering what kind of model u are using in this current source configuration? Is Vbb directly connected to ground? Also, what's the supply voltage source? How will it different if I have a different Vdd, I mean in terms of W/L ratio of both device? Thanks!
wondering what kind of model u are using in this current source configuration? Is Vbb directly connected to ground? Also, what's the supply voltage source? How will it different if I have a different Vdd, I mean in terms of W/L ratio of both device? Thanks!
The supply voltage is connected at the right side to R13, Vdd
The current generated in the left path is intended to be used as current source
1, The current is different when there is a different Vdd
2, the current also increases as W/L of both devices increases, because the current=Vgs(MN39)/R14, when W/L increases, Vgs(MN39) increases. But the change of current is not very significant