Effect of series resistor at the gate of current mirror

[jamesbond939]

Hi all,

I notice for some current mirror implementation includes a series resistor that is connected to the gate of the diode-connected transistor of the current mirror.

May I know the the purpose of the series resistor?

Thanks a lot.

 

[windknows]

hi, i've seen this circuit in a book talking about current-mode design longtime ago
if i'm right, the R here is to increase the bandwidth, the pole will change and it also add a zero.
you can calculate the small signal transfer func from the input current to the voltage of the M2 gate

 

[mustansirm]

A paper explains this design well
Search for :"A Novel High Speed Current Mirror Compensation Technique and Application" by T. Voo and C. Toumazou

 

[dick_freebird]

By lagging the feedback FET, you will add peaking / sharpness
to the rest of the mirror rack. This can of course be overdone.