What's the difference between this circuit and one with MP11

[jutek]

circuit's name

hello

does this circuit have a special name??

what's the role of mn13. it's a level shifter which shifts min1 drain's voltage down about VGS(mn13)

but why? what's the difference between this circuit and "normal" with MP11 diode connected?

thanks

regards

 

[engp6482]

Re: circuit's name

Maybe the headroom will be increased a little

 

[pixel]

Re: circuit's name

In the case of simple current mirror mp11 pmos always works in saturation because vdg=0<Vtp. Vdp11 drain voltage is defined by current and size of M11.
If Vdp goes too low (small m11 or high m11 current) it can limit maximal input voltage to Vdd-Vsg11+Vtn < Vdd (input transistor goes in saturation).

Vgs13 makes that pmos is always in triode region, because Vdg=Vgs13>Vtp.
In this case vdp11 and input voltage are not limited and can go up to Vdd.